Popular Science Monthly/Volume 28/February 1886/Acclimatization
| ACCLIMATIZATION.[1] |
By Professor RUDOLPH VIRCHOW.
IT is a well-known fact that the influence of a strange climate upon the emigrant, however little the new medium may differ from the mother-country in more or less essential qualities, exhibits itself at first in a kind of recrudescence of vigor, which, however, in a very short time, sometimes after a few days, gives place to a general languor. Days, weeks, or months, according to the degree of healthfulness of the place, may pass before the organism is again in equilibrium; and this fact is so generally recognized that every traveler expects it and prepares for it. A person just landed in a distant country would be chargeable with imprudence if he neglected the precautions which experience has prescribed for diminishing as much as possible the inconveniences of this critical period. What does this mean? Simply that the organization of the new-comer must bring itself into harmony with the new medium. It makes no difference that he finds in the strange climate, in the European hotels, comforts, fare, and attentions so perfect as almost to make him forget that he has ever left his native land; he has, all the same, to go through the change which the climate works in his organism. He must adapt himself to it, become used to the new conditions. The fact of this process going on was known a long time before Darwin came into the world; and there is not, so far as I know, any doctor who has interpreted it in any other way than as a physical modification of the organism which is not limited to some superficial trait acquired by the transplanted person, but notably modifies the mechanism of the vital functions.
Two kinds of effects accompany the course of acclimatization: first, simple discomfort or climatic indisposition; and, afterward, illness proper or climatic illness. Danger, as distinguished from simple inconvenience, is the element that characterizes climatic illness. The invasion of the disease is real only in so far as the existence, or the integrity at least, of the whole organism is threatened. Till this moment, we have only indisposition to deal with; although, to speak accurately, illness and indisposition are not separated by clearly defined limits, but are rather two degrees of intensity of the same manifestation. A person is ill in the evening who was only indisposed in the morning.
If we review the vast literature that has accumulated on this subject, we shall be obliged to confess that original labors respecting these special modifications are almost wholly wanting. On the other hand, as soon as illness appears, the interest, which has now become immediate, excites the ardor of physicians; and they, by their numerous researches in this branch of the subject have given us knowledge, not only of what are generally the diseases of foreign regions, but also of their immediate causes. And, while there are still a few points in dispute, the increasing extension of wisely directed medical studies, at home and abroad, gives a well-founded hope that they will shortly be settled. Otherwise the condition of foreign medicine is but little different from that of our own; and there is no doubt that, with the progress of science, the clinics of tropical maladies will acquire an equally important development.
Our knowledge of the facts relative to climatic indispositions is not what it ought to be, and yet there are some respecting which information is particularly important to us. Inasmuch as a transformation of the organism constitutes the principal element of a durable acclimatization, it is not the individual alone who is affected by a prolonged sojourn away from his native country, but his entire posterity as well. We can not, therefore, deny that this side of the question is the most important of all. There is one point of view from which the study of the transformations acquires a general interest of really vast extent. It is that of their relations with the history of the human race. Two questions occur at once to all who seek to arrive at a clear idea of the manner in which man has reached his present condition. Is it true that the different human races and varieties are issues from a common stock? And what are the causes of their diversity? It is of no use for our friends the zoölogists to preach transformism to us. That may do very well of itself when we have only an affair of building up a system. But, unfortunately, no man has ever yet observed the transformation from one race to another. No one has, for example, seen a people of the white race become black under the tropics, or negroes transplanted to the polar regions or to Canada metamorphosed into whites. The question whether color is related to climate still remains to be solved, experimentally at least; data bearing on the subject are still absolutely wanting. I confess that, if any one should ask me for the slightest light respecting the origin of races, I should not be in a condition to give a plausible argument or an experimental fact that would be competent to justify any point of view whatever. It is nevertheless true that, at the bottom of every impartial study of the phenomena of acclimatization, we arrive inevitably at the old point of view of Hippocrates, and that the existence of a relation between the somatic properties of man and certain geographical circumscriptions is not doubtful. That is what my friend Bastian understands by the term ethnological provinces. The reality of such provinces is incontestable; and they have the same significance with reference to man as zoölogical and botanical provinces in the geographical distribution of plants and animals. We can not deny that we have also the right to premise the existence of general laws of acclimatization which apply to plants and animals as well as to man—at least so far as regards the modifications of classes.
The prime question for us relates to the aptitude which the white man has manifested for acclimatization through all his historical evolution. To what point have we a right to conclude, from the data furnished by history, that the white man can find, outside of the limits of his country, conditions favorable to his existence? To bring up the vital point of the problem at once, the white man is not everywhere the same. Scientific experiment is every day tending to bring into more prominent relief the sharp differences in this matter which exist among the different subdivisions of the white race which we ordinarily ordinarily include under a common denomination. Between the Aryan and Semitic branches, for example, the contrast is very clear. All the statistical documents and all the observations at large (grands traits) that have been made to this day go to confirm the greatly superior power of acclimatization of the Semitic to the Aryan peoples. The latter peoples may also be divided; and it is easy to separate those varieties with different aptitudes into geographical groups. The peoples of the south, the Portuguese, the Spaniards, the Maltese, and the Sicilians, are much superior to those of the north—so much so that the choice of one or another of these elements might be of decisive importance for the success of a colonizing enterprise.
In this may be found the solution of the controversy into which I have been drawn in the course of political debates. The fact is, that the history of the colonization of the Antilles shows us that, in the French and English establishments, the results of colonization have always been disastrous for immigrants from Europe, while in the Spanish colonies the results have been relatively favorable, although not so favorable as my adversaries have wished to make them appear.
These general observations must not, however, be accepted without reservation. They as yet represent only the starting-point of the discussion which it remains for us to bring to bear upon two capital questions. The first of these questions is concerning the opinion, which seems at the outset extremely plausible, that immigration into regions near the tropics, or even under the tropics, is nearly harmless to peoples who are natives of southern latitudes. Nothing is further from being proved, as we may see by referring to the negroes, whom it is very difficult to remove safely from one tropical country to another. The French in Senegal have had sad experience of this fact, and have seen death make terrible ravages among black populations which they had transplanted from their native land.
Another consideration that it is important not to lose sight of is that the farther south we go the more have the Aryan branches been exposed to foreign admixtures. The Maltese race, for example, exhibits a much superior resistance to the Sicilian or the southern Spanish race. We might be tempted to explain this by the insular situation of the former race, and by the character of the climate of its country. In that case the Maltese, transported to the African Continent, for instance, to a considerable distance from the coast, having come out from a climate distinctly insular, might be supposed to feel the change more profoundly than a Spaniard coming from his more continental climate. But nothing of the kind takes place. Algerian statistics establish most positively that the Maltese constantly holds his overwhelming superiority in adaptability over the Spaniard.
So the explanation of the special power of resistance shown by this race can not be based entirely upon an agreement of the climate of its native country with that of the place to which it emigrates. There must, then, enter into the account some favorable circumstances derived from the mixture of foreign blood which it carries in its veins. This foreign blood is chiefly Semitic. As is well known, the Phœnicians, a people having more than one point of analogy with the maritime powers of our own days, were the first colonizers known in history. The Phœnicians were Semites; and archæological traces of their establishments are still to be found in Malta. They founded Carthage, and covered the Spanish coast with colonies, which probably extended for a considerable distance into the interior of the country. As the latest archæological researches prove, they colonized a good part of Greece. Their influence was so great, and their extension was so wide, that it would have been very strange if they had not contracted in Spain and elsewhere numerous family connections, and thus made their blood participate in the development of the races which have survived them in those countries. In less ancient times, most of the Iberian Peninsula was for hundreds of years in the power of the Arabs, or rather of Moors from Africa. These conquerors, who founded large cities and peopled entire districts, so that the Valencian garden and the valley of Granada still retain their Moorish aspect, who, in short, spread themselves over the whole country, undoubtedly left a numerous posterity behind them. And as the Spanish language is full of Moorish reminiscences, and Arabic words still adorn its vocabulary, how can the nation count the descendants of those Moors who hide their Semitic origin under Spanish names?
The race which now peoples those countries is, therefore, a mixed one; and there is no nation, even to us Germans, that has not furnished its quota to it. The Visigoths passed through Spain. They were dissolved there, and so completely absorbed that not a vestige of them is left, except, perhaps, in the institutions in which the most eminent Spaniards acknowledge, not without a feeling of gratitude, the contribution of Germanic genius to the development of their nation. Thus, from this fusion of Iberians, Phœnicians, Moors, Romans, Celts, and Visigoths, to which may be added, perhaps, a few other German elements, such as the Alani, has risen the modern Spanish people, a mixed people, in the elements of which the pure Aryan race enters in part, but is nowise preponderant. If, now, we should undertake to say, “Wherever a Spaniard can go I can go too, for the same blood flows in the veins of both of us,” we should be in great error. No; Spanish blood is not the same as flows in our veins; no more than is the blood of the Hindoos of to-day, with whom we have but lately tried to make a common ancestry, but whom no one now regards as a primitive race. We now trace our affiliation to that people which, coming down from the north, was crossed, higher classes and all, with the people that occupied the peninsula long before the arrival of the conquerors, and who were black.
There are, then, mixed races, to a certain extent more mixed than we can observe among ourselves. It is, nevertheless, indisputable that, compared with the races in which the Aryan element has been observed in its purity, those races, especially those which have drawn largely from the Semitic fountain, are incomparably more fitted to acclimatize themselves, and propagate themselves in the midst of the new conditions in which they are placed in hot countries. In order to include under a more characteristic denomination those races which are only slightly refractory to the morbid influences of the climate, races to which we ourselves belong, I proposed, on a former occasion, to call them vulnerable races. This figurative expression might serve, in the domain of pathological ethnology, to designate the property which those races have of going through grave alterations under the influence of relatively slight external causes; and, considered in the narrower domain of acclimatization, the facility with which, among them, indisposition puts on the aspect of real illness. There is, however, a very limited zone within which these vulnerable races can implant and propagate themselves with comparative security. North America holds the first place in this favorable zone. Here we see the curious phenomenon of the French in Canada, the same northern French who are melting like wax in the sun of Algeria, becoming, from the little colony which they were in the beginning of the century, a vigorous and numerous people, and lively enough to hold their own against the rising tide of English immigration; while tens and tens of thousands of our countrymen, whom America receives annually at her ports, disappear in a very short time. In Canada, the colonists of French origin, animated by the most lively spirit of independence, have constituted themselves a people apart, and the last conflict, which has just closed, is a convincing proof of the tenacity of their national feeling.
Then comes the United States, with its vigorous and constantly increasing population. However much it may be mixed, it will always be Aryan at the bottom, for all the heterogeneous elements are absorbed, almost without leaving traces of themselves, in that immense hearth of colonization, which has no parallel in history. The English have been no less happy in the settlement of Australia, a colonization the energetic expansion of which has not been checked except toward the north, where the conditions grow unfavorable as the settlements approach the equator. Hence it comes that, in the northern part of Queensland, European colonists are not in a condition to endure the fatigue of agricultural labor. This fact has had much to do with the efforts made of late years to annex New Guinea and New Britain, whence it has been proposed to draw the manual forces required for the tillage of the soil.
In the South African colonies the Dutch have been solidly established for some two hundred years; and, in a few countries of South America, colonies composed of peoples of various European origin have prospered, though unequally. There are also some young colonies founded by Germans on the Rio Grande, in Brazil, which a fancy still needing confirmation has placed in the rank of healthful countries and suitable for our people. Reviewing the results that have been obtained in the colonies thus briefly enumerated, which embrace the sum of the more or less fortunate enterprises of the kind, we see that their success has been in inverse proportion to the difference in isothermic latitude between them and the mother-country of the colonists. But in every case it is not probable that the organization of the colonists has escaped having to pay, at the expense of profound alterations, for acclimatization in foreign countries. Men of science, as well as tourists, have been interested for many years in the study of the Yankee type, which, according to the general opinion, is not wholly comparable either with the English or the German, or with a cross of the two with the Irish race. The peculiar physiology of the Yankee is yet to be made out, and I can not insist too strongly on the great value of the scientific results that might accrue from the study of this delicate ethnological problem. It is averred that the transformations of this type grow more pronounced as we go from the Northern to the Southern States.
It sometimes occurs that a population transplanted into a distant country remains apparently stationary. Nothing seems to distinguish it from the compatriots which it has left in its native country. But, on regarding it more closely, we find that there is operating within it one of the gravest phenomena in the history of colonization—a phenomenon which has been long observed in animals and plants when transported to new climates: a decrease of fecundity and an arrest of development, going at length to the complete elimination of posterity. It is evident that the condition most essential to the prosperity of a colony, the only guarantee of its longevity, resides in the number of children in the families of the settlers; children who, in their turn, the source of posterity, lead, as at home, to the branching out of every family into numerous ramifications. The further we advance into exotic climates, the more rapidly does the diminution of the reproductive faculty of the colonist go on, the more do statistics indicate a reduction in the number of births and an increasing sterility in successive generations. This fact has been noticed not only by doctors, who have called attention to it from time immemorial, but persons also who could have no prejudice in the matter—statesmen, military men, literary men, and men of every profession and every country, and those who lived in times when the question had not yet begun to be the order of the day—have observed for the most diverse countries that families formerly fertile, but who contracted alliances exclusively with natives of the exotic countries, lasted only a few generations.
It has never been possible, even to this day, to establish a durable colonization in British India. It has, indeed, been said recently that it is possible, by means of severe hygienic processes, successfully to bring up an English generation there; but to do this the children have, as soon as they are able to support the journey, say at five or six years of age, to be taken to the mountains and left there till they are fifteen or sixteen years old. This reminds me of the palm-trees which we succeed in making bear fruit in our gardens. Because, by the use of the most elaborate horticulture we can occasionally cause a plant of the most delicate species to mature its fruit, shall we venture to regard the palm-tree as acclimated in our country? No more can we assert as much of a population which has no chance of maintaining itself except by taking all its children to the mountains and not allowing them to come down thence till they are mature men. A curious kind of family life that, and extremely costly if it were undertaken, the results of which are limited to bringing down the young generation, which is destined to live in the country, from the north to the south, from the mountains to the plain, like the ancient kings of Persia. But the indefatigable perseverance which has been applied for years in organizing this system does not in any way look to the colonization of India. It only seeks to create a new higher class, an aristocracy, which shall be better qualified to govern the country than annual new arrivals from England. I will also observe that the Dutch in Java and their other Eastern establishments have not advanced the problem a step. Every considerable family endeavors to send its children as soon as possible not merely to the mountains, but to Europe, more for physical conservation than for education. As a whole, these attempts at colonization singularly remind us of the fate of the Lombards in Italy. Those people, it is true, survived a little longer on the conquered territory; but very few centuries were sufficient to reduce them to the state of hardly appreciable vestiges. And for the Goths, it did not require a hundred years to annihilate them completely in that same Italy. Minute statistical researches have, it is true, quite recently brought to light here and there a few traces of the Lombards, and it is in a similar way not improbable that there may still exist in the country a very little of the ancient Germanic blood; but in upper Italy there does not remain any well-defined posterity; and in the northern provinces of Portugal and Spain, where the Visigoths reigned in all their power, it would be just as useless to look for any clearly appreciable posterity of the conquerors. I was recently accused of not being willing to range Italy and Spain among the countries favorable to the settlement of families originating in the lands of the North. I am sorry for it, but I can not perceive any facts that make it probable that our countrymen can settle in those states with any expectation of leaving an enduring posterity. I am ready to bow to the proof when it is brought forward. I would also suggest to our physicians of the navy and the merchant marine, and to all who travel for any purpose, that it would be a profitable task to prepare in the most scientific form, and the one most fitted to aid investigations, the existing data bearing on this point.
What, then, to be precise, is the evil which threatens colonial populations, at first sight so little different from our own, and of which no external sign is apparent to reveal very profound transformations? The most powerful agent in producing degeneration, and to which doctors always give the first place, is the reduction of the formation of the blood in the organism. Is there really a retardation of this function, or an exaggerated destruction of the blood? I can not take the responsibility of deciding. Whatever it may be, emigrants are attacked with the same affection as in its phase of complete development among us is called anæmia. The more existence is tried by debilitating influences, the more intense becomes tropical anæmia.
But important as is its part, these debilitating influences do not consist of malaria alone, with its accompaniments of intermittent and other pernicious fevers, dysenteries, and liver-complaints; for even those whom the fever spares are not protected from tropical anæmia. The microscope has revealed to us many other morbid agents. Worms swarm in the tropics, particularly in the water, from which they pass to the body of man; and some of them abide in the blood. All such parasites may become destructive agents to the economy, which is subjected to a decline, the first manifestation of which is always impoverishment of the blood. With all our knowledge of the physiology of the blood, we are not yet able to explain, on the ground of merely theoretical data, the enormous loss of that liquid. We may admit that the preponderant part belongs to the destruction of the blood, while the absorption of air and oxygen is not increased.
A remarkable symptom, which is very well explained by an active destruction of the blood, is the strong predisposition to liver-disease. The liver is an organ the relation of which with the physiology of the blood is very intimate, and the troubles of which have the most influence upon the constitution of that liquid; and that is the organ which is the first object of the attacks, not only of malaria, but of the common diseases of acclimatization.
If I linger on these examples, it is to render more moving and more convincing the appeal which I make to doctors and naturalists to apply themselves to this sphere of research. Neither the French nor the English have as yet done anything important with reference to it. It is, then, a virgin field that falls to German science. It is also a subject of the highest importance; for we can not think of even an approximative solution of the problem till we have gained a precise idea of the modifications of the organism, and particularly of the special alterations of each organ, which are connected with the phenomena of acclimatization.
The popular masses, in their carelessness, seek the acquisition of gold. Show it to them, and they will plunge into perils without concerning themselves about the rules of acclimatization and its diseases, any more than a starving man asks about the sanitary qualities of a ham that is offered to him.
The question before us is not of an isolated enterprise, but of very extensive ones, and is of interest to the empire as well as to the great companies which are lending their aid to emigration. Great problems must be resolved, in order that we may in the future be in a situation to inform our colonists respecting the fate which awaits them, to found colonies with a foresight of what the probable results will be, and to send emigrants into distant countries under, the choice of circumstances which will permit them to hope for an assured existence.
These are questions which no general, war minister, or statesman has a right to evade. Why should it be different with those at whose invitation battalions of emigrants leave their country? There is New Guinea, with its rich plains and immense forests coming down to the river-banks. It is no longer a question of sending there only specialists to discover the most profitable timber-trees and then found business establishments. Just as in the last century, when the French desired to colonize Cayenne; what beautiful descriptions did they give of the fertile country, with its luxuriant flora, its wonderful forests, and its ravishing prairies! When the thousands and thousands of colonists who were sent there had perished to the last man, the French settled down to admire the photographs of those wonderful forests and stay quietly at home, leaving to those whose ethnological province is in Cayenne the task of propagating themselves and attending to their affairs. I have no doubt that we shall soon be forced to follow this example, and I hope that the frankness with which I declare this conviction will prompt us all to fulfill the duty which this great popular movement imposes upon naturalists and physicians. It is our duty to take hold of the question and organize the study of it, and to arm ourselves with scientific methods for the exploration of these distant countries, and for ascertaining to what point a permanent colonization in them is possible.
We need more than isolated examples to satisfy ourselves of the adaptability of the white race to fix itself in this or that place. A peculiar population exists in the mountainous region of the Island of Réunion, called “petits blancs” or little whites, who have been ascertained to be the last remains of the French colonists who established themselves in that part of the island a great many years ago. Recently a French traveler discovered in the Vindhya Mountains, in India, some survivors of a French colony which was founded there three centuries ago. There is nothing impossible in these facts; but they singularly remind us of the exotic conifers which are planted in our experimental forests. Now and then a forester has a success with one of them, and the little plant becomes an object of curiosity to travelers and the people of the neighborhood. But the number of these plants is insignificant. They are isolated examples or rarities, and no particular importance can be attached to them.
All these facts, I repeat, only make us feel more keenly how desirable it would be to determine scientifically the conditions which make the existence of our vulnerable race on a foreign land possible. We might then direct our emigrants with the same certainty as that with which a modern captain, who knows their wants, provides for his troops. As I look at it, I can not regard the mission of naturalists and physicians toward their nation as conscientiously performed till a satisfactory solution is given to this problem.
- ↑ From an address before the Congress of German Naturalists and Physicians, at Strasburg, September 22, 1885.