Popular Science Monthly/Volume 48/March 1896/Acclimatization I
By WILLIAM Z. RIPLEY,
ASSISTANT PROFESSOR OF SOCIOLOGY AND ECONOMICS IN THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY.
THERE is no question of greater significance for European civilization than the one which concerns the possibility of its extension over that major part of the earth which is yet the home of barbarism or savagery. The rapid increase of the Aryan populations is more and more forcing it to the forefront as a great economic problem. No longer is it merely a scientific and abstract problem of secondary importance as contributory to the theories of the unity or plurality of the human race. It has today become a matter of peculiar significance for the present generation of men, and the old abstractions, which did so much to confuse its students, are laid aside. The substantial unity of the species having become an accepted fact along with the doctrine of evolution, the migration and consequent acclimatization of the various branches of the parent stock follow as a matter of course. The modern problem plainly stated is this: First, can a single generation of European emigrants live? and, secondly, living, can they perpetuate their kind in the equatorial regions of the earth? Finally, if the Aryan race is able permanently so to sustain itself, will it still be able to preserve its peculiar civilization in these lands; or must it revert to the barbarian stage of modern slavery—of a servile native population, which alone in those climates can work and live? An area of fertile lands six times as great as that cultivated by the people of Europe to-day stands waiting to absorb its surplus population. But its point of saturation will obviously soon be reached if traders and superintendents of native labor are the only colonists who can live there. Moreover, the problem of acclimatization has a great political importance; for if any one of these European nations be possessed of a special physiological immunity in face of the perils of tropical colonization, the balance of power may be seriously disturbed. Or a great menace to the feeble attempts of Europeans to colonize the tropics may exist in the surpassing aptitude of the great Mongol horde, which is perhaps the most gifted race of all in its power of accommodation to new climatic conditions. Africa, Polynesia, and all parts of the earth have now been divided among the nations of Europe. What will they be able to do with them, now that the explorer has finished his work? Because the problem pertains to the sciences of physiology and of anthropology, in no wise lessens its concrete importance for the economist and the statesman.
Before we are in a position to measure even approximately the influence of a change of climate upon the human body and its functions, a number of subordinate confusing factors must be eliminated. Neglect to observe this rule vitiates much of the testimony of observers in the field. In the first place, a change of residence in itself always tends to upset the regular habits of the soldier or the colonist. The temperate youth in England becomes a heavy drinker in the barracks of India; and the Portuguese and Spanish races, predisposed to the use of light wines—ready even to give up the habit if need be—suffer from the disorders incident to alcoholism far less than the English. Inflammation of the liver is indigenous to the tropics; and yet the ofttimes six-fold deadliness of hepatitis among English soldiers in India, compared with the mortality among the native troops from the same disease, is probably due more to the consumption of alcoholic drinks than to the influence of the climate. To this fact is also
due a certain immunity of the wives and children of soldiers in this regard. A moderate amount of alcoholic stimulant undoubtedly has a beneficent action. Dr. Clarke even asserts that light wine is an indispensable part of a hygienic diet; but the abuse of the drinking habit is a factor in the comparative immunities of all races in the tropics not to be neglected.
Alcoholism and sexual immorality go hand in hand. Newly acquired vicious habits, unknown amid the restraints of home life, would speedily cause physical prostration in any climate. An engineer in Algeria testifies that "a Sunday will put more men in the hospital than three days in the hot sun." One of the most subtle physiological effects of a tropical climate is a surexcitation of the sexual organs, which in the presence of a native servile and morally undeveloped population often leads to excesses even at a tender age. The elimination of this factor becomes especially important in dealing with the crossing of races and the effects of climate upon fecundity. It is invariably true that the mulatto—a social as well as an ethnic hybrid—suffers from a loss of caste which exposes this class to many temptations. The effect of this upon morbidity can not but be very great in face of the peculiarly weakened physical resistance. Among the imported and liberated negroes in the West Indies, indeed, immorality rises to a climax almost sufficient to outweigh every other consideration.
The influence of national habits in the choice of food is a third element to be eliminated. One of the immediate effects of a tropical climate is a stimulation of the appetite, which too often leads to overindulgence. On the other hand, it seems to be rather the kind than the quality of food which is the decisive factor. Dr. Felkin advises an increase in the daily allowance, provided it be of the right sort. In this regard the Teutonic nations are especially handicapped in competition with the Mediterranean peoples. The English and Germans insist upon their usual allowance of meat, where the Spaniards or Italians are content with cereals or lighter food. The Chinese are especially favored in accommodation to a new tropical climate by reason of their simple diet of rice.
More important even than food, as a correction to be applied, is the effect of daily habits of life and of profession upon the physiological processes.
An indolent life always and everywhere tends to superinduce a multitude of disorders. De Quatrefages has pointed out that in the West Indies the wealthy and idle Creoles, and not the "petit blancs," swell the death-rate of the white population above the average. Gentle and regular exercise, then, must be accounted one of the most important hygienic precautions to be observed. Worse than lack of exercise, however, is overexertion, especially if it be coupled with exposure to the hot sun or to miasmatic exhalations. Statistics for the Jewish race, confining all its activities to shops in the towns, must be corrected, therefore, for this circumstance, before they are compared with statistics for the Germans, who as colonists take up the ever-deadly cultivation of the soil. The Boers, who thrive as herders, would undoubtedly suffer were they to stir up the soil as husbandmen. Most favored of all is that nationality which is seafaring by nature. The apparently high vitality of the Italians and Maltese in Algeria is in part because they are mainly sailors and fishermen.In consonance with this principle is the relative immunity, already cited, of the wives and children of soldiers in India. Slavery also always produces a terrific death-rate which vitiates all comparison between the statistics for the white and the negro. It should be noted, moreover, that such an institution exercises a selective choice upon the negro; for the survivors of such severe treatment will generally be a picked lot, which ought to exhibit vitality to a marked degree, all the weaklings having been removed. Racial comparisons are also invalidated by the fact that hygiene and sanitation are generally confined to the European populations, so that, other things being equal, a higher death-rate among the natives would be most natural.
In any scientific discussion of the effect of climate upon the human body the racial element must always be considered; and correction must be made for ethnic peculiarities before any definite conclusions become possible.
Three diseases are peculiar to the white race and to civilization—namely, consumption, syphilis, and alcoholism, there being marked differences in the predisposition of each of the barbarous races for them, which often vary inversely with the degree of civilization they have attained; so that their widely varying liability to contract these diseases becomes an important consideration in the ingrafting of any degree of culture or of artificial life upon the native inhabitants of a colonial possession.
The Aryan race in its liability to consumption stands midway between the Mongol and the negro, climatic conditions being equal. The immunity of the Ural-Altaic stock in this respect is very remarkable. The Kirghis of the steppes, exposed to the severest climatic changes, are rarely affected with it, and the pure Turanian stock is almost exempt from its ravages. This may be one reason why the Chinese are able to colonize in many places even in the tropics where the negro can not live, since it is well known that a tropical climate is fatal to all persons with a consumptive tendency. The Chinese succeed in Guiana, where the white can not live; and they thrive from Mamiatchin, where the mean temperature is below freezing, to Singapore on the equator. That their immunity from phthisis is due in large measure to race, and not to climatic circumstances, seems to be indicated by the results of ethnic intermixture. The Japanese apparently derive a liability to it from their Malay blood, which not even their Turanian descent can counteract. The Malays, a mixed race, seem to lack vitality in many other respects as well, in all of which the Japanese share to some extent. Their liability to consumption seems to be akin to that penchant for alcoholism, which is lacking among the Chinese because of the national opium habit.
The negro even in the tropics is especially subject to all affections of the lungs, a fact which constitutes a serious bar to his wide extension over what has been designated by Dr. Fuchs the catarrhal zone, in contradistinction to the dysenteric zone of the tropics. The black races have in general less fully developed chests and less respiratory power than the European race. They perspire less freely, and their skin is thicker, or at least more dense, so that oxygenation by the lungs alone is more necessary. They are consequently exceedingly sensitive to atmospheric changes, and are severely handicapped in any migration for this reason. Almost invariably, where the European succumbs to bilious or intestinal disorders, the negro falls a victim to diseases of the lungs even in the tropics. An interesting case is instanced of a caravan in Senegal, composed of ninety-five negroes and ninety Europeans, in which the average mortality for each of the two contingents was exactly equal for two years. Yet only one of the whites was affected with disease of the lungs, while five of the eleven negroes who died succumbed to diseases of this class. Similar to the effect of change of climate upon the negro in inducing respiratory derangement is the influence exerted by altitude, which will be discussed in another place.
Dr. Ashmead has suggested an interesting reason for the predisposition of the negro for consumption—namely, that the broad, open nostril of the race is unfitted to perform the necessary service of warming the air before its entrance into the lungs. Leptorrhinism, he asserts, is due to natural selection, which has fixed upon that form of nose as most suitable to the temperate zone; and the negro, deprived of this advantage, suffers from disease of the lungs at once he is transferred to that part of the earth. It is not inconceivable that this may indeed serve as a partial explanation, but how, then, can we account for the equally open nostril of the Turanian stock so immune from consumption? Or how can this theory be made to square with the predisposition of the Polynesian for the same class of diseases, especially when the leptorrhinism of this latter race is taken into account? At all events, this element of race must be reckoned with in every comparison of the statistics of different localities.
In the geographical distribution of diseases there is no more uncertain factor than the ethnic peculiarities of syphilis. It can therefore never be neglected in any project for acclimatization by crossing with the natives, since its relation to fertility is so important. Probably brought by the Aryan race to America and to New Guinea, and by it disseminated in Polynesia, this disease seems to be as yet unknown in Central Africa to any extent. In fact, it dies out naturally in the interior of that continent even when introduced, while it kills the American aborigines at sight, From this dread disease the Chinese are especially exempt; for if contracted, it speedily becomes benign, in marked contrast to the Japanese, who betray their Malay blood in this respect. Everywhere syphilis follows the Malay stock even in crossing with other races, like the negroid, which by nature is immune, as has been said. In Madagascar, where five sixths of a certain population was infected, Hirsch declares that the Malagasy (negroid) element is quite free from it, the Hovas (Malay cross) having it in the severest form.
It will at once appear that these ethnic peculiarities of syphilis are of the greatest importance, therefore, since this disease is likely to prevail among exactly those classes in a colonial population where ethnic crossing would be most likely to occur. Intermixture as a remedy for acclimatization would consequently be much more difficult of application in the East Indies or in South America than in Cochin China or the Congo Valley; for where this malady strikes down the first cross—the mulatto or the half-breed—all further assimilation of the races is at an end.
The list of ethnic diseases might be greatly extended, but enough has perhaps been said to indicate the importance of eliminating it before entering upon the discussion of acclimatization per se. The predisposition of the negro for elephantiasis and tetanus, his sole liability to the sleeping sickness, so severe that in some localities the black is utterly useless as a soldier, his immunity from cancer and his liability to skin diseases in general, together with his immunity from yellow fever and bilious disorders, are well-recognized facts in anthropology. The Mongolian type appears to be likewise free from inflammatory diseases, and oftentimes from cholera to some extent; as well as from beriberi, which is so peculiar to the Malay stock that it may be traced in the Japanese kak ké. The Polynesians are immune from scarlet fever, and it is said that the Japanese can not even be inoculated with it. This again is an illustration of the same persistence of pathological predispositions, since the partial affinity of the Japanese to the Polynesian race is well established. Modern investigation is bringing out similar examples of the constancy of racial diseases among the modern peoples of Europe. Dr. Chibret affirms that the Celtic type is immune from "trachoma," or epidemic granular conjunctivitis, which has often seriously ravaged the rest of Europe.* Spreading in the Belgian army, it passed over the Walloons; and in the central plateau of France attacking strangers alone; it passed over southern Bavaria, even when contracted by a Celt, speedily becoming benign. The only exception to this racial immunity is that of the Piedmontese, otherwise it never extends above the two hundred metre Celtic boundary. Always, in accounting for such a phenomenon, two factors are to be considered—race and environment. Hence, in our study of climatic circumstances the first must be carefully eliminated before proceeding to study the second.
Finally, the effects of ethnic intermarriage or crossing must in every case be taken into account. It is present as a complication in almost all colonial populations, and is by far the most subtle and difficult of all eliminations to be made. Notwithstanding the objection that accommodation to climate by intermarriage is in reality not acclimatization at all, but the formation of an entirely new type, the two are continually confused; and crossing with native stocks is persistently brought forward as a mode and policy of action. As an element in colonization, and a devious means of avoiding the necessity of acclimatization, it arises to complicate the situation. Intermarriage is said to be the secret of Spanish and Portuguese success; in Mexico this has apparently been the case, as well as in the Philippines. Dr. Bordier states that the Spanish and southern French are more prolific than others in marriage with negroes; and concludes that the only hope for the future of French colonization in Cochin China lies in such crossing with the natives. The efficacy of this remedy is to-day accepted quite generally by anthropologists. Topinard agrees with Ten Kate that half-breeds resist climatic changes better than pure whites, and other authorities concede the same. Desmartis has even proposed to inoculate the British troops in India with Hindu blood as a preventive of tropical disorders.
On the other hand, a cross between races is too often apt to be a weakling, sharing in the pathological predispositions of each of its parent stocks, while enjoying but imperfectly their several immunities, as we have seen.
Mulattoes in any climate are liable to lack vitality, and especially, unless a continual supply of white blood is kept up, they tend to degenerate. Dr. Gould notices this lack of vitality among mulattoes as very marked in the Union army. For this reason intermixture is by many regarded as a doubtful remedy. Neither the Malay nor the Japanese mixed races have the vitality of the Chinese. Jousset affirms that in many cases crossing increases the liability to attacks of fever. In Guiana the negroes thrive, but the mulattoes suffer from the climate. Berenger-Ferand states that the mulatto in Senegal so far degenerates as to become infertile after three generations; and Westermarck, while acknowledging that many statements of this kind are exaggerated, inclines to the view that crossing may be unfavorable to fertility. Be this as it may, it is certain that mulattoes are pathologically intermediate between the white and the negro; they rarely have yellow fever, and are less liable to malaria (paludism) than the Europeans; and they are not predisposed to bilious disorders. But they have all the diseases to which the negro is alone liable—namely, elephantiasis leprosy, phthisis, and even the dreaded sleeping sickness (mal de sommeil). Finally, it may be added that many of the most successful examples of acclimatization have occurred where there has been a complete absence of crossing, as among the Jews in the Bourbon Islands, with the Boers in South Africa, and in many parts of South America.
The physical elements of climate, ranged in the order of their importance, are humidity, heat, and lack of variety.
Heat by itself, when unaccompanied by excessive humidity, does not seriously affect human health except when unduly extended. The ranges of temperature to which the human body may become accustomed are very broad, so that the limitations to the dispersion of the race seem to be set by the food supply rather than the degree of heat or cold. All authorities agree, therefore, that the regions where acclimatization is most difficult are to be found in the areas of excessive humidity, or, roughly, where there is the maximum rainfall. For this reason the successful examples adduced in favor of the view that acclimatization in the tropics is possible, should always be examined in the light of this consideration.
A traveler in northern Africa has noted this in his observation, that "where there is water and something can grow, there the climate is murderous; where the climate is healthy, there is no water and nothing can grow." In this sense, the boasted acclimatization of the French in Algeria is merely accommodation to one element of climate, after all. With this limitation it will be generally conceded that the success of the French in their African possessions along the Mediterranean is assured. The mortality of soldiers and sailors in Algeria was seventy-seven pro mille from 1837 to 1848, so that Boudin, Bertillon, and Knox doubted if the French could ever colonize there. At the present time the birth-rate even exceeds that in France itself; and the death-rate is but little above the normal. In Tunis also the birth-rate was 35·6 pro mille in 1890-'92, greatly exceeding the ruling death-rate of 25·7 per thousand. In America it is in the uplands of Mexico, Peru, and Bolivia, or along the arid coast of the Pacific, and not in the real tropical climate of Brazil, where the Spaniards have succeeded most fully. They have also done well in Cuba, to be sure, but the cases are entirely dissimilar. And to reason, from the French success in Algeria, that the same would ensue in the Congo basin, in Madagascar, or in Cochin China is totally to misconceive the real limitations of a tropical climate. The relative difficulties to be encountered in these several cases may be roughly indicated by the mortality of soldiers. In Cochin China it is almost exactly double that in Tunis; and this is, roughly speaking, a measure of the difference between a mere torrid climate as distinguished from one which is very humid as well as hot, for humidity means that malaria is superadded to all the other difficulties inherent in climate alone.
The heat in a tropical climate becomes important but indirectly, because it is the cause of humidity and generally accompanies it. In the temperate regions humidity goes with cool weather except in the dog days, while within the tropics heat prevails just when radiation through perspiration is most retarded by moisture in the atmosphere. This, in combination with the enforced lack of exercise and its attendant excretion, forms the double cause of physiologic disturbances. The blood is not properly purified and anæmia ensues, if the more immediate effects do. not manifest themselves in intestinal disorders.
Everything which conduces to give a variety to the climate of the tropics affords relief. The alternating sea and land breezes of islands make them more amenable to European civilization. Especially when these islands are volcanic or mountainous is the strength of these tempering elements increased. This, in fact, is the only alleviating circumstance in Jamaica, where the fierce sea breezes by day, reversing at night, have made life for the English possible. Singapore owes its prosperity to the fact that it is the only place in the East Indies where malaria is completely unknown. Similarly, wherever there are alternating seasons of heat and cold, the chance of acclimatization becomes greater. Hence one advantage of the climate of plateaus in the tropics, since both daily and seasonal variations are very great. Even in the major part of the African plateau, however, the elevation can not overset the monotony of the tropical climate, the seasonal variations ranging much lower than ours, while the mean temperature is fifty per cent higher.
Altitude, while giving at least temporary relief to the white race, seems to exert a peculiarly baneful effect upon the negro and the Indian. Dr. Spruce gives an interesting example of great economic distress produced by it in South America. Coffee grows in the zone from four thousand to six thousand feet, and the demand for native labor is very great. Indians coming from above die of dysentery, while if they come from the coast they succumb to respiratory diseases, so that the planters are severely hampered. It is said in our Southern States that the negro can not go from the hill country to the plains without great physiologic disturbance. Jousset declares that the elevation of three thousand to forty-five hundred feet proves fatal to the negro in Africa. This, of course, is due in part to the greater sensitiveness of all primitive peoples to climatic changes, and partly due to lack of hygiene. But that the negro by nature really lacks a power of accommodation, even in the tropics, in this respect is conceded by most observers;<ref>Vide discussion in the Bulletin de la Société d'Anthropologie, i, p. 528; Hunt, op. cit., p. 131; Jousset, p. 148; Ratzel, i, p. 304. Cf. the case of Apaches in Alabama given in the Publications of the American Statistical Society, September, 1893. immunities he once enjoyed, and does not thereby gain any new ones. A project to import twenty thousand negroes from Alabama and Mississippi into the State of Durango in Mexico has been definitely abandoned, after the payment of over one hundred thousand dollars for freight charges alone. The land companies will introduce Chinamen instead, and the outlook is correspondingly brighter. Every experiment but demonstrates more clearly that the negro is useless as a colonist, even for reintroduction into the tropics,