Problems in the Colonization and Settlement of Tropical South America

Problems in the Colonization and

Settlement of Tropical South America*

For the present paper I chose a subject which needed no previous literary researches, impossible to accomplish in a short time, while I could fall back on my personal observations and an experience acquired during many years in different parts of Brazil, a country which owns the greatest share of tropical South America, and is fairly typical for the rest.

Only part of the country limited by two tropics owns a really tropical climate, which implies an average annual temperature of not less, and generally more, than 21° centigrade, while the daily observations often mark more than 30° in the shade and may come within a few degrees below blood heat. This torrid zone may extend beyond the tropics, but between them it is limited to low vertical elevations, as the average temperature rapidly diminishes with increasing altitude, at a rate of about one degree for every thousand feet. Where there are high mountains after climbing a few thousand feet we may reach a delightful climate, but if we continue to ascend, we encounter quite unpleasantly cool and cold places. An aviator, starting in a tropical country for a high altitude record, would soon experience arctic cold, while the spectators were still stewing in tropical heat.

Even before the advent of Europeans, what there existed of higher culture in tropical America was localized in countries where cooler mountain climates were available for the capitals. Such conditions are outside the question we attempt to explain, to wit, that is why such large extents of tropical country should continue to be undeveloped while the population of the earth is steadily increasing, so that several countries are already congested, and clamor for expansion complaining under the plea that their food production is not progressing, while their population is augmenting. Humanity is like a large family, crowded in an enormous house of which many rooms are not used.

This paradox, like so many others, is explained by historical and political conditions. Humanity is not a united family which might distribute the unoccupied rooms among its members, according to their common interests, but rather resembles a family in which most of the members think only of themselves and are always ready to quarrel with the others about their pretended rights, besides looking down with contempt on their poorer relations.

Tropical America has a very interesting pre-Columbian history, the investigation of which is making great progress, due in large part to North American scientists and corporations. However, after the advent of Columbus the whites did not trouble much about the rights of their primitive American relations, whom they despised as heathen. They claimed practically the whole of the newly discovered lands, although some of these had to be conquered first. By decree of the pope, South America was divided between the Spaniards and Portuguese by a boundary line which is still respected.

The problem to which tropical America belongs is actually solved. Not even the most unknown parts are unclaimed, while quite a number had two claimants, as the limits indicated by hardly known rivers and by faulty maps were not well defined. Of late, most litigation has been finally decided, although some still remains in existence. Even some states of the same country have their

“contestados”.1

According to the customs of their time, the Spaniards and Portuguese kept the new possessions strictly for themselves, looking upon them as a source or revenue for the king and an occasion of enriching his protégés. The principal object was to gather from the inhabitants as much gold, silver and precious stones as possible, and to discover new mines. Those treasures were for the most part claimed by the crown, to whom they brought large revenues, although a great part of them were intercepted in times of war. Agriculture, though indispensable as a means of support for the soldiers and the other people in the service of the crowns, was not considered as the principal end. By using the information of the natives and their methods of traveling, the unknown countries were explored, in the hope of discovering mineral wealth. The

“bandeirantes”, 2 who often had Indian mothers and spoke their language, lived in Indian fashion during their expeditions. These lasted for many months, sometimes even for years, and led to a general knowledge of the explored regions. The tropical forests, which yielded no mineral wealth, were little explored and only along some of the rivers.

The Indians were also employed to do the necessary work, but they were not greatly to be relied upon, even under compulsion. This led to the introduction of Negro slaves, who showed more endurance and greater aptitude for hard work. They added a new element to the ethnological collection, which was further varied by frequent cross-breeding. The pure whites and those who pretended to be such, despised manual labor, which was considered an attribute of slavery. The Negroes certainly had a very large share in the opening the country while slavery lasted, but after its abolition they showed little inclination for going on with the work.

Except in some restricted countries, the Indian element lost its importance with the advent of the Negroes. In the more progressive parts, the Indians tended to vanish, partly owing to their slight resistance to diseases. In most places genuine Indians are never seen now, except for deputations of tribes from the interior, and then they form an object of curiosity; nevertheless, many members of the population still show some traces of Indian features. The genuine Indians, tame or wild, are found only in remote places, where, of late, tribes have been discovered who still lived in the Stone Age, while other unknown tribes may exist even now. The Indian languages are known only to scientists, or to people directly dealing with the tribes. They are hard to learn and very varied. In Paraguay alone, where the population is in great part composed of Indians, a kind of “guarany,” which the Jesuits introduced as a general language, is still commonly spoken. On the river Paraná the Jesuits gathered large numbers of Indians under their protection and organization. These settlements were quite prosperous, until the attacks of slave hunters caused the Indians to migrate down the river, where large numbers of them succumbed to malaria. The organizations dissolved when the Jesuits were expelled, although missionary work on a smaller scale is still done by other orders in some remote parts of tropical Brazil.

The mother countries treated their American colonies in a rather step-motherly way, giving only scant consideration to the interests of the permanent inhabitants. Owing to the great distances and the dangerous journeys, no king of Spain or Portugal ever visited them until Don João VI, through fear of Napoleon, transferred his court from Lisbon to Rio de Janeiro. After his return his place was taken by his son, who afterwards, under pressure, declared the independence of Brazil. The Spanish colonies also got separated from their mother country little more than a century ago, so that the whole of South America, with the exception of the Guianas, became independent. Some former attempts of the French and Dutch to settle in Brazil ended with their final defeat by the Portuguese; but the Dutch began the scientific investigation of the country and some of their racial features are still found amongst the population of the region which they formerly occupied.

The three Guianas, although colonies of highly cultivated nations, do not seem to develop rapidly, because of the climate and other difficulties which have not yet been solved.

The Latin republics, to which Brazil has belonged since 1889, would not think of abandoning their rights to the land, and it is evident for them that the development of tropical South America must come. However, none of them is suffering from overcrowding. On the contrary, most of them have parts which are still undeveloped, although they have milder climates, and are often less distant, promising better remuneration with less danger to health.

Since the establishment of independence the dog-in-the-manger policy has to a large extent been abandoned. Free transoceanic navigation and international trade, the development of mineral resources, the opening of railway lines, the improvement in seaports, and the organization of many kinds of industries, have brought a large infusion of foreigners, some of whom have become naturalized and founded families. Foreign descent is shown throughout Latin America by many names, even of statesmen, although political rights are of course limited to citizens. However, naturalization is easily obtained and comes automatically to the children of foreigners born in the country.

Even before the complete extinction of slavery about fifty years ago, some South American states tried colonization with foreign elements, recruited from the poorer classes of European nations, with the double aim of furnishing working hands to the plantations and of forming an independent class of small farmers, which might supply the towns with their products. As in other places too much attention was paid to the number and too little to the quality of the immigrants, but the final result was that the states which received the most colonists are to-day the most flourishing. However, all of these states enjoy favorable climatic conditions. The torrid zone received few immigrants, and in some of the warmer places colonization failed through unhygienic conditions. Just now, the Japanese are investigating the region of the Amazon with a view to colonization, and it will be interesting to learn what they think of it. In British Guyana and in Trinidad there are many Hindoos who, at least in the latter place, seem to do well. They may easily find it an improvement on some of their own countries.

Large parts of the tropical coast line of Brazil offer relatively favorable climatic conditions, being cooled by almost constant breezes. As there is a number of good natural seaports within easy access, through which the imports and exports have to pass, quite a number of larger and smaller towns have developed. These were for the most part founded long ago and have a history. Bahia was the first capital, and Pernambuco was developed by the Dutch. As impenetrable forests were not prevalent, most of the zone being rather dry, communication with the interior was not so difficult to establish. In some parts, rivers formed an easy way of access. Now there are several railways of considerable length in connection with the landways and waterways of the interior, which extend to quite distant zones. The landways used for mule caravans, called “tropas,” and for the transport of cattle are generally pretty bad and become impassable after heavy rains, but we are now at the beginning of development of automobile roads and their extension is one of the problems of the future, together with the development of the railway system and of river navigation.

It is not generally known that a considerable part of northern Brazil is rather dry and subject to periodical droughts, which at long intervals may assume the character of tremendous catastrophes, when the cattle die for want of water and food, and the starving inhabitants have to emigrate in large numbers, in order to save their lives. This happens principally in the state of Ceará. Although the emigrants might abandon these regions and settle in safer places, they generally end by returning.

Great quantities of food supplies and large sums of money have to be spent on such occasions, and the mortality, aggravated by epidemic diseases, is very large. To meet the expenses, the whole country has to contribute, since the individual states are not rich enough, and it is often difficult for help to come in time.

The federal government has spent great sums on the problem of preventing such catastrophes, by establishing barrages to retain the water in the rainy seasons, and by digging wells and by opening means of communication. The question of dry farming has also been considered. However, there remains for all the dry regions the sanitary problem of keeping the drinking water from pollution, as the limited water supply in dry seasons is used promiscuously for all purposes and is open to every contamination. This has already led to the prevalence of Schistosomum Mansoni in those regions, and the prevention of this and other diseases due to contamination of the water supply must become an essential part in the sanitary program of the future.

The São Francisco River, even in dry times, carries a considerable quantity of water, but close to the river there is an arid zone, which produces very little and almost seems a desert. As in Egypt, some cultivating is done, after the annual inundation, on the banks and islands which have been submerged; but, unlike the situation in Egypt, there is no general irrigation. I have traveled on the main river and its tributaries to a great extent. Some of the banks are less arid, but only the Rio Corrente, in which the strong current permitted the use or waterwheels, was used for irrigation. The results were extremely good and the formerly almost treeless land became covered with trees and vegetation, showing what could be accomplished in other places.

From Pirapora to a point beyond the junction with the Rio das Velhas, the banks of the river are still normally covered with green vegetation, but then they become progressively more barren, although, strangely enough, some writers speak of this country as most fertile. On the lower part of the course which is mostly made in sternwheelers, wind is almost constant and could be used as power for irrigation. Here we see an extensive formation of sandbanks and dunes, while the water, which higher up is very muddy, becomes somewhat clearer.

Pirapora, where the navigation begins, is connected with Rio de Janeiro by a railway of 1,000 kilometers in length, while Juazeiro, where it ends, is connected with Bahia by another long line running through some very arid country. The tributaries of the São Francisco River drain a very extensive region, which transports its various products by means of them. One cannot help thinking that the production ought to be much larger, if proper irrigation was used. The population in the numerous small towns along the river is mostly poor, with predominating black elements, showing little desire and capacity for progress. If a big corporation started irrigation and planting on a large scale together with canneries for fish and fruit, and established a few good roads, the country might become very flourishing. However, this would require much more capital than could be furnished by the native population.

Here is a region, situated well within the tropics, between the eighth and thirteenth parallels, which, when developed, could support a much larger population than at present. With proper sanitary control, it might be made tolerably healthy. Below Juazeiro the river does not allow steam navigation, and finally, after a still long course, it forms the celebrated fall, or rather falls, of Paulo Afonso, where any amount of power could be obtained without spoiling the picturesque effect of this quite unparalleled cataract. This marvel of nature ought to be made more accessible to tourists who wish to appreciate its full beauty. Below the falls there is a short railway, joining the river where it again becomes navigable for smaller craft, which alone are capable of passing the somewhat dangerous bar at the mouth of the river.

While the dry countries of the northern part of Brazil, although insufficiently developed, are nevertheless known and are accessible by the ordinary ways of traveling, conditions are very different in the vast tropical rain-forest, which surrounds the Amazon and its tributaries, apparently unbroken and with very little vertical elevation. Here the maps show only a dendritic system of affluents of all sizes. A certain number of small towns and settlements, bearing in part Portuguese, in part Indian, and in part saints’ names, are grouped for the most part along the larger and more navigable rivers, but not close together. At a distance from the rivers, no names appear on the maps, since all the intervening space is practically unknown.

The problem of surveying those nearly unknown zones seemed hopelessly difficult only a short time ago, but the use of aerial navigation, and of photography, makes the solution comparatively easy. The last Hamilton-Rice expedition was the first to use a hydroplane, with very satisfactory results; and of late, Pinedo, went in one flight over the territory where a strategic telegraph line had been established a few years before at an enormous outlay of time, work and money. It should soon be possible not only to correct the existing maps as to the courses of the rivers, but in particular to

ascertain the distribution of forest and campos,3 swamps, plateaus and hills, in order to devise new ways of communication with some of the most remote places.

In the forest country mineral riches were not available, nor was there any agriculture. The vegetable products, among them some valuable

drugs, were all obtained by 4 “industria extractiva”, which means the gathering of nature's spontaneous offerings, generally distributed over a large expanse, which is difficult of access. Among these, rubber proved to be the most important, so long as it fetched high prices. The rubber trees, belonging to the genus Siphonia and various species, not all equally valuable, grow along the riverbanks from Pará upwards to widely remote tributaries, mingled with other vegetation and never in large groups. The hope of finding new and good locations has led to a general knowledge of those rivers which were not too much obstructed by rapids, but not, as a rule, to permanent settlements. All the traveling was done by water, and only at high water could many of the places be reached, even by small craft. If they failed to return in time, owing to some unusual conditions, the crew was obliged to wait for the next year's high water. This happened so often that they went already prepared to make plantations, in order to get the necessary food supply.

Navigation by sail, oar, or punting was necessarily slow, while the distances were often enormous. The foodstuffs, which formed the base of alimentation, were generally inadequate and the prices of the most common articles increased with the distance. Conditions generally were very much as they used to be in the gold fields. While traders and the governments made a great deal of money from the high prices of rubber, the unfortunate rubber gatherers often spent more than they earned. As the latter could not leave without paying for the necessities of life, obtained on credit at very high prices, many of them remained practically in a state of slavery without any hope of improvement, besides being the victims of the prevalent diseases. When the monopoly of rubber was lost and the prices went down, there was a general state of depression, and many places were abandoned. The remedy might be found in siphonia plantations, like those of Ceylon, where they have given good results, but the expense and the risk are believed to be too great; also such plantations would have to be located near to the centers of population. Unless the prices improve much or some other profitable “industria extractativa”turns up, there seems to exist no incentive for further development, or even for the keeping up of the most remote, and more or less temporary, settlements.

On the Amazon itself and on some of the larger tributaries, there is of course steam navigation, mostly carried on by national companies. Foreign navigation was not permitted in former times, and even now only a few transoceanic steamers run up to Manaus. The places between Pará and Manaus were not at all up to date when I last saw them. The climate is very warm all the year round and there is little to make life comfortable. Manaus contains only a few streets which might be transplanted from a modern city.

The river Amazon is very wide, but comparatively shallow, and by no means so easy to navigate as might be expected. There is no perceptible current between the mouth and Manaus, except at Óbidos, where the river is narrowed at low water to a width of 800 meters with proportional depth. The influence of the tide extends all the way up, a distance of over 860 miles. The water is always muddy, so that the bottom cannot be seen, even in shallow places. Islands of all sizes, some of them very long, are exceedingly common, so that both banks are rarely seen, and even then are very distant one from the other. There are considerable floods, so that all the piers must have at least two stories, and houses near the river are built on poles. The high water brings considerable changes by excavating the higher banks and carrying away parts of them, together with the trees which grow on them. The channels are perpetually changing, and the unbroken and monotonous vegetation which covers all the land makes orientation difficult for any one who does not thoroughly know the river. Even the steamer journey from Pará to Manaus still takes several days, and in traveling to more remote places by smaller craft, as Wallace, Bates and Spruce did in their well-described journeys, the amount of time spent is enormous. The total length of the Amazon alone is considered to be about 3,000 miles.

River navigation might be much improved through circumventing the rapids by railways, roads or channels, blowing up obstructions, and employing fast boats with flat bottoms and aerial propellers, instead of the present sternwheelers burning wood. In more prosperous times hydroplanes might come into general use.

There are practically no railways to shorten the enormous distances in Amazônia. A short line is running from Pará to the Atlantic coast through a rather favorable country. Another was begun near Alcobaça and there is a third one going round the falls of the Madeira, to give the Mamoré navigation from Bolivia an outlet on the Amazon. Both of them had to contend with difficulties similar to those met by the Panama railway.

The river is still the only means of communication. Horses are kept only on cattle ranches, as on the isle of Marajó. These had to be constantly renewed, as they succumbed to the Mal de cadeiras, a trypanosomiasis of the capivaras, transmitted from them by horseflies. The capivara (Hydrochoerus capibara) is by far the largest rodent, attaining the size of a hog and quite amphibious. It is very prolific, and becomes quite numerous when not persecuted. The horses used to come from the island of Caviana, where the disease was not prevalent. With the extermination of the capivaras, and treatment by modern methods, the disease might be kept down; but the horses cannot be used in the forest region for want of food, and would be useless without roads.

For the moment there is only one railway projected to connect Rio de Janeiro with the Amazon by way of Pirapora. The São Francisco River is already bridged over, and the preliminary exploration has long since been done. The work is not expected to progress very quickly and will not affect the opening of the unknown forest region, although it may furnish some valuable experience.

The opportunity of telegraphing by cable or communicating by railway is already quite fair, and the wireless telegraph seems especially invented for communicating over unexplored countries. The benefit of these institutions might be increased by lowering the charges.

With a large number of people employed in the industria extractiva, in trade, and in navigation, the Amazon region has never produced enough foodstuffs to make importation unnecessary. Travelers in more remote places often find it difficult to obtain anything, except the poorest and most monotonous diet, so that beriberi was extremely prevalent. It is characteristic that chickens had to be imported and were sold at very high prices, even in Manaus, although they generally represent one of the principal resources of most settlers in tropical countries. Vegetable products, so easy to grow in the tropics, never formed an article of exportation, except in the case of cacao, which was not used at the places of its production. Brazil nuts form an article of local consumption and of exportation, but also belong to the industria extractiva. The

castanheiro 5 is one of the tallest wild forest trees. I have not heard of attempts to make plantations of this tree which might give results only after a very long time. While mentioning the industria extractiva, one might as well ask why the woods themselves should not be more exploited. There is no doubt that if half the forest zone could be converted into roads, paths and clearings, the other half would benefit exceedingly, while enormous quantities of timber, firewood, charcoal and paperpulp might be obtained. At present, the precious woods for cabinet work, which may be admired in exhibitions and in the palace of the president of Pará, are obtainable only in limited quantities; for in the Amazonian forests, with the exception of some palms and a few species of no value, the same kind of tree is never found in large groups nor near to the waterline, where, however, firewood may always be bad. Even to obtain a good dugout, it is sometimes necessary to cut a long path from the river through jungle and forest, causing more work than the canoe itself. Any clearing, when not kept up, will in a few years be overgrown by jungle, while a path cut through the woods will take even less time to become impassable. The only way to keep up a clearing for agricultural purposes is still to cut down all the vegetation with the axe, let it dry as much as possible, and then set fire to it. On the ground covered with ashes and charred wood the first cultivating is done with the hoe, while the stumps and fallen trees are slowly rotting away. As any new plantation generally requires this preliminary work, and as agricultural machinery cannot be used, the small amount of tilled ground is easily explained. Better methods of exploiting the forests and clearing the ground constitute another problem of the future, the solution of which may, however, be expected with confidence.

As for animal products, there are a great many cattle raised on Marajó, on the low lands along the banks of the Amazon and in the region of the Rio Branco, which are shipped alive to Manaus and Pará. The pastures are not good, being subjected to drought and inundation, which cause the animals to perish in great numbers. The financial returns, however, are good, because the expenses are very small. Crossbreeding with the large Mysore zebus has given good results. Cattle raising is limited to the campos and llanos, also known as savannas or prairies, which are found for the most part to the north of the forest zone.

The campos or llanos, which have a dryer climate, are easier to explore and healthier than the forest zone. Still, they do not seem to progress rapidly. The principal industry is the raising of cattle and horses, which demands much space when the pastures are not of superior quality. In some of these places we find the same problems as on the São Francisco.

In this connection I might mention still a fourth zone, which in some parts is quite developed; we may call it the swamp region. Actually, this is for the most part avoided. If the malaria problem becomes solved, these places might be used for the extensive cultivation of rice, which in some places already exists in a wild state. With it, it might be combined the raising of ducks, following Chinese methods.

Besides being the only way of locomotion, the Amazon and its tributaries furnish also most of the animal food of local origin. The game, even with good native hunters, is not so much to be relied upon and besides it is for the most part found only near the water. The best supply of fresh meat is provided by the big turtles, which on certain occasions are collected on land in numbers and can be kept alive for any length of time. Their meat is wholesome, and even very good; and so too are the eggs, but it would be preferable not to collect these, as the plundering of their nesting-places leads to the rapid diminution of the turtles. There is also the pirarucu, a big fish of the size of the tunny, which, like the turtles, is caught when in the water by shooting it with arrows, so constructed as to form a sort of harpoon. The meat is rather coarse, but is dried in great quantities and often used as a staple food, although it meets with little approval from the consumers. There are better fishes, which are often caught in great quantities, but do not keep so well as the pirarucu. To prevent the extermination of the turtles, and to preserve some of the fishes in a more perfect way may be considered another problem of the future.

After this rapid and incomplete sketch of the conditions prevalent in tropical South America, we may inquire into some of the principal obstacles to progress. The first of these is always the climate, which we are unable to change, though we may mitigate its effects. While in our case, life is rarely threatened, heatstroke and similar conditions being rarer than in hot summers of many regions of the moderately warm zones, there is no doubt that the continual heat has an unfavorable effect on white men by producing excessive transpiration, which leads to prickly heat, continual thirst, loss of sleep and appetite, followed by neurasthenia. These appear for the most part at times and places with prevalent moist heat and warm nights, not relieved by cooling winds. White people can hardly be excepted to reach their full bodily and mental capacity in places where mere existence is difficult. Though I do not doubt that they may maintain themselves unmixed through various generations, circumstances of a sanitary, social and economical nature have generally prevented the experiment, and isolated cases do not permit the drawing of conclusions. I have seen two white polar bears, kept in the zoological garden of Rio de Janeiro for years, and while admiring their faculty of adaptation, I should not consider them fit for tropical life.

For indoor work conditions may be so much improved as to make it comparatively easy, but much depends on local resources. Cooling the houses in warm countries is just as important as heating them in cold climates. The problem of the dwellings is to obtain the maximum of ventilation with the minimum of insulation. Artificial cooling does not show much progress at present, but its improvement is one of the problems of the future. The most appropriate manner of clothing must be studied and it ought not to be influenced by fashion. Where hills or mountains are within easy reach, the families may live there and the working members may return after the day's work. The seat of the government, of large enterprises and of health resorts may be located in similar places. Where those are not available, leave of absence might be given periodically, in order to give relief from the continual heat.

Good bathing arrangements, ventilators and a liberal supply of ice may mitigate the effects of the climate to a large extent.

Whoever is finally expected to do the work must be given a certain amount of comfort and satisfaction in his possessions. Appropriate, nice-looking cottages or houses must substitute for the mud buildings which, unless whitewashed inside and outside, always look disreputable and harbor vermin, sometimes of a dangerous nature. Barefoot walking is risky in many ways. The water supply must be good and must be kept uncontaminated; appropriate privies, and washing and bathing arrangements are of the highest necessity to keep up sanitary conditions. Ambition for a higher standard of life must be cultivated, principally among the younger generations for which end schools and cinematic demonstrations may be used. Although the improvements above mentioned are just as desirable in cooler climates, their necessity is there more generally known, while their neglect is less fatal. It is only right that some of the progress should come from the places where it is most urgent, just as the studies on tropical diseases benefit other countries, where the same diseases exist without prevailing to a similar extent.

The problem of obtaining a good water supply, or at least pure water for drinking, must be solved according to circumstances, by using springs, simple or artesian wells, and as a last resort by filtering, individually or collectively. Under critical conditions, it is better to discard the use of unboiled water for tea and coffee and to use imported, still or aerated, drinks. This advice is meant for the traveler, because the inhabitants generally are not exacting, but drink with great enjoyment the water on which they navigate, or, worse still, get it from the shore, where the animals enter for drinking and bathing and where all the washing is done. The worse the conditions, the less they seem to mind them. It is true, as it has frequently been pointed out, that the evil effects of this are not necessarily evident, but an importation of cholera or typhoid fever soon shows the fallacy of that argument, as I have had occasion to witness.

Of all the problems in the development of tropical America none is more important than the prevention of certain highly fatal diseases, not so much those which are peculiar to, or restricted to the tropics, as those which are especially prevalent in hot countries. Although not a necessary consequence of high temperatures, they are nevertheless dependent upon them. So long as the real cause and the way of spreading of these diseases were not known, but were subject to erroneous theories and speculations, all the sanitary methods adopted proved insufficient. However, the last fifty years have gradually led to such phenomenal advances in our knowledge, that we may soon be able to consider the tropical diseases as the most accessible to prevention and cure.

Nowadays the parasites that produce tropical diseases are for the most part known and can be seen under the microscope when they circulate in the blood, thus confirming the diagnosis. Many of these organisms, adapted to the heat of the human body, require a temperature not much inferior to that of the blood, when they leave it, to undergo further evolution. This takes place in some bloodsucking insect or tick, the temperature of which corresponds to that of the air. When this is not warm enough, development is interrupted or altogether stopped. The tropics are more affected in this respect, because bloodsucking insects are active there all the year round, while the temperature does not drop below the critical point. In moderately warm climates the favorable temperatures last only part of the year and the epidemics show spontaneous interruptions.

In warm countries people may harbor in their tissues a small and very thin roundworm capable of remaining in the lymphatic or blood vessels. It is now known as Filaria Bancrofti. The larvae are found in the circulating blood, but, curiously enough, only at night time. Considering the possibilities of their leaving the body without drying up, Manson, while in China, discovered this periodicity, which reminded him of the time of activity observed in the most common house-mosquito. He soon verified further states of evolution in the mosquito, when it had absorbed human blood with larvae, and Bancroft, in Australia, completed the life-cycle by showing that the full grown larvae reached the mouth-parts of the mosquito, and invaded the human body, on the occasion of the next bite.

This observation, wonderful in itself, became the starting point for a succession of other brilliant discoveries in human and animal pathology, made by an army of investigators of many countries. Today there are many handbooks and periodicals dedicated to tropical medicine, which is taught as a postgraduate discipline in several schools of different countries. In connection with it, protozoology developed as a branch of importance, helminthology and entomology added new chapters to their investigations, while parasitology and medical zoology became collective disciplines to an extent previously unexpected.

The notion that parasites of the human blood might depend for their evolution and transmission on mosquitoes and other bloodsucking insects or ticks, in the first instance added to our knowledge of malaria, caused by protozoa, which infect the red blood-corpuscles. Their animal nature was first recognized by Laveran in Algiers. Subsequently, several Italian scientists extend his observations and led to the establishment of three species, found also in America and distinguished by their morphology and by the symptoms which they produce. The most deadly form of malaria is especially prevalent in the tropics. Ross established that the transmission of malaria parasites, found in men and in an allied species of birds, was accomplished by mosquitoes serving as intermediate hosts, while Grassi showed that in human malaria the transmitters belong to the genus Anopheles. Of that genus many species are known all over the world, being generally divided into many genera, which form the subfamily Anophelinae. All of these are more or less under suspicion, but no other mosquitoes capable of carrying the infection have been discovered. Most of the Anophelinae breed in stagnant water, in swampy or periodically inundated regions, but the malaria of mountain forests is transmitted by a species breeding in the water collected in epiphytic plants, as I was first able to show in Brazil.

There are many ways of attacking the problem of tropical malaria: by the treatment and isolation of the patients; by protecting healthy persons from the bites of infected mosquitoes; by destroying the breeding-places of the larvae, by drainage or by filling up the swamps, by the removal of aquatic vegetation, and by stocking with small fishes; by covering the surface of the water with a film of petrol; by treating the water with aniline dyes or other substance which poison the larvae; not to mention some more theoretical proposals. According to circumstances, they all may prove useful, but all of them together are not sufficient to guarantee the sanitation of a place under really difficult circumstances. Quinine does not cure the chronic cases which cause the infections; screens are expensive, perishable and inappropriate for the places where the poor people sleep; mosquito nets make the temperature unbearable on really hot nights and the anti-larval measures can be used only on a small scale. Intelligent people living in well screened houses may escape infection, even where malaria is prevalent, but for the poorer classes inhabiting periodically inundated countries, a successful anti-malarial campaign depends on the finding of a remedy which will cure the chronic infections, as well as the acute ones. The speedy solution of this problem of experimental therapeutics might come any day, considering the present activity in trying new chemical compositions.

More circumscribed foci of malaria in well administrated places may be made to disappear by drainage, by filling up pools or treating them with larvicides, as shown in Lagos and at the canal of Panama, both of which places had a very bad record and are situated well within the tropics. Clearing away of threes and jungle has driven out malaria from some places that I know. Rigorous exclusion of all infected workmen by medical examination ought to be the first step in all large undertakings, such as railway, road and bridge building, even in uninhabited countries, which through want of these and other precautions regularly lead to epidemic malaria. Prophylactic administration of quinine, and screening or disinfecting the sleeping quarters, where possible, may contribute to save the situation. The contractors must be made responsible for the sanitary measures.

Yellow fever is the most deadly infection transmitted by the mosquitoes. It was always noted that this disease was not directly contagious and did not spread in places where the temperature was relatively low, due to vertical elevation. In other places the epidemics ceased in the colder-season and reappeared with the heat. Foreigners were especially subject to it, while many natives seemed to acquire immunity, independent of a manifest attack. All the hunting for the responsible germ, in which I myself spent much time, had given no practical result, as happened in other diseases attributed to organisms too small to be perceived, even with the microscope. Disinfection, avoiding the drinking of water from the local supply and the prophylactic use of arsenic preparations proved of no avail. The possibility of a certain kind of mosquito being connected with the disease was pointed out at least twice, the last time by Finlay in Cuba; but his experiments, made in an infected region, were not sufficiently convincing. However, his intuition was afterwards proved to be right by a commission investigating the disease in Cuba, though mostly composed of North Americans. By this time the idea of mosquito transmission had become more familiar and I, for one, accepted it at once, as I had gathered very strong circumstantial evidence in the first epidemic of Campinas, in the state of São Paulo. At my suggestion mosquito prophylaxis was established in the epidemic centers of this state (where I was director of the Bacteriological Institute) and an illustrated description of the yellow fever mosquito was published. However, a repetition of the experiments in Cuba was considered desirable. Of five volunteers bitten by mosquitoes infected from the same patient three had yellow fever symptoms; the director of the sanitary department and myself showed immunity acquired without manifest attack. Other ways of contamination gave a negative result, as in Cuba. Finally a French Commission from the Pasteur Institute studied the question more extensively in Rio de Janeiro and their results were considered final.

The first of the long standing endemic centers to become free from yellow fever by mosquito prophylaxis was Havana, due to the activity of Gorgas, and the next was Rio de Janeiro, where Oswaldo Cruz successfully overcame all the obstacles. Since then, yellow fever has rapidly diminished, and its last hiding places are being watched by the Rockefeller Commission and by the local authorities. In my opinion, it will still take a long time of assiduous watching to get rid of every remnant, but, at any rate, the disease has ceased to be an obstacle to the settlement of the tropical countries, at least in our hemisphere, despite what might happen, if it should be carried to the other side of the globe where dense populations and mosquitoes abound, is quite another question.

Dengue is another epidemic disease, transmitted by the same kind of mosquito, and beginning with the same symptoms. As its mortality is practically nil, its transmission has been extensively tested on human beings, positive results being constant where there was no previous attack. We must familiarize ourselves with the idea that, at least in the tropics, infectious diseases are just as likely to be transmitted by bloodsucking insects, as by contact or by infection of the water.

As I have explained on another occasion, leprosy in its spreading behaves just like yellow fever, the difference being of course that the latter is an acute disease, while leprosy is an eminently chronic one. The circumstantial evidence of the mosquito transmission of leprosy is overwhelming, but the experimental proof cannot be given until a safe cure, or a susceptible animal is found. One might expect that the mere suspicion ought to be sufficient to make the admittedly desirable mosquito prophylaxis obligatory in the treatment and sanitary regulation of leprosy; but so slowly does the human mind adapt itself to new ideas, that this is not even seriously thought of by most of the people who consider themselves leprologists.

The long list of diseases transmitted by bloodsucking insects in the tropics, or outside of them, is steadily increasing and comprises also some of the most deadly diseases of domestic animals. To enter into a description of most of them would lead too far, but this much we learned in the last decades and principally during the war, that what people used to call vermin are still more objectionable from the sanitary than from the aesthetic point of view, and that mosquitoes, sandflies, blackflies, gadflies, ticks and fleas are not only nuisances, but really dangerous. For this reason the study of all these temporary parasites has become quite an extensive science, to which I have dedicated a considerable part of the last thirty years. Insects and ticks, sucking the lymph or blood of man and domestic animals, are very numerous and may be rated at several hundred species in the warmer part of South America. What gives these studies a special interest and value is their relation to diseases, not only of man, but also of the most important domestic animals. The investigation of animal diseases has contributed enormously to the understanding of human pathology, while the morphological, and principally biological studies of the temporary parasites has become one of the most interesting chapters of entomology.

There is, however, a large number of tropical diseases that are not related to insects, but that are due to the contamination of soil and water by human excrements. Some of these are connected with protozoa living in the intestines. The most important is the Endamoeba histolytica, producing a kind of dysentery and sometimes abscesses of the liver, now fortunately quite amenable to medical treatment. Others are due to worms and of these the so-called Ankylostomiasis, or hookworm disease, is the most prevalent. Although curable by several methods, its ultimate extinction will be obtained only by sanitary reforms, which means breaking whole populations from inveterate habits. As it is generally known, the Rockefeller Commission has been working in this line for years in many countries, in combination with local authorities. As the disease is mostly acquired by walking barefoot on infected soil, the use of boots or shoes is a real necessity. These will also afford a protection against sandfleas, against infections following accidental wounds such as tropical ulcer, and also against snake bites.

The list of problems is not exhausted, but I trust that a general idea of the most important ones has been given. I have not stated new facts, but have tried to recall and emphasize the special difficulties connected with the development of new regions. This will come of itself when it is really needed, but the process is necessarily slow. Thus we gain time for educating new generations and introducing many of the improvements which we may confidently expect from the general and rapid progress of humanity.

I have limited my discussion to the conditions in tropical South America, because I knew, though not being an ocular witness, of the splendid work the United Fruit Company has already done in Central America. It has given a practical demonstration of what may be achieved in developing new countries, when the medical and sanitary part of the task is duly considered.

* Reprinted from the Bicentenary Number of the American Philosophical Society's Proceedings, v.LXVI, 1927. Paper read on April 28, 1927. Republished by Kaiserlich Leopoldinischen Deutschen Akademie der Naturforscher in Leopoldin: Amerika, Leipzig, Verlag von Quelle & Meyer, 1929, ser. 2, v.4, p.306-19. [E.N.]

1 Reference to the Contestado War (1912-1916), a conflict between government troops and the population of an inland region in the states of Santa Catarina and Paraná that was claimed – or ‘contestada’ – by both States. The government interference was motivated by the peasant movement started in the region by the Messiah-like leader-healer José Maria, who preached against the laws of the newly proclaimed Republic (1889) and foretold the advent of an Utopian Monarchy, the reign of peace, abundance and justice. [E.N.]

2 Men that participated in military expeditions to the inland – bandeiras – to explore the wild lands, to search for precious minerals and to capture Indians for slavery in Colonial Brazil. [E.N.]

3 Fields. [E.N.]

4 Extraction industry. [E.N.]

5 Lutz probably refers to Brazil-nut tree. [E.N.]