III. If organism, operating normally among different races, presents such varieties, why can we not suppose that it would hence show correlative differences in its morbid changes? should there not be, also, an ethnic pathology? This contains a large question, and yet it was scarcely thought of a few years ago. It seems to have been first proposed and studied by F. Schnurrer in his treatise on _Geographical Pathology_,[154] in 1813, in which the author seems to have perceived imperfectly, in all its vastness, the matter which now occupies our attention. The book is divided into three parts; the first is entirely geographical, the second entirely anthropological, and the third is given up to a description of maladies, commencing with two introductory chapters; the first describing the diseases of each zone, and the second, containing eleven pages, is a “Glance at the general Characteristics of Disease in each Race.” “In fact,” says Dr. Boudin,[155] in pointing out the novelty of these enquiries, “there are some races who show themselves completely rebellious to certain pathological forms, for which others, on the contrary, show a remarkable pre-disposition.” Two particular maladies have been pointed out in this point of view,--_marsh-poisoning_ in all its forms, and _yellow fever_. Africans are evidently, at least in parts, exempt from these two diseases, which only attack them with a very minor force. It has been said that the question of marsh-poisoning is still very doubtful; it was allowed that the Negroes were less exposed to its attacks than other men, but it was desired to enter the question of acclimatisation[156] into the calculation of facts. All the countries we know that are inhabited by blacks, being nearly all subject to the noxious influence of marshes, it was pretended that even stranger Negroes had acquired from infancy, in their own country, an immunity by which they benefited later in life, and even had the power of handing it down to their descendants.[157] It is thus that some have explained, for instance, the unhappy results of the English expedition to the Niger in 1841. Out of 145 whites belonging to the crews, the three vessels, after a navigation of about forty-nine days on the river, had lost 40 men (130 were attacked). Out of the twenty-five coloured men embarked in England, and who were mostly born in America, eleven were seized with illness, but not one of them died.[158] This individual acclimatisation can only be either a fiction, or a proof in support of the ideas which we defend. In the presence of a morbid influence which shows itself and continues, two things alone can happen,--either destruction, or permanent (that is to say, _specific_) modifications of œconomy, in harmony with the ordinary manner in which this animal population continues to exist.