Man's existence depends upon physical surroundings; these surroundings have exercised an immense influence in modifying his organism, in shaping his social development, in moulding his character. To enumerate all the external factors operating upon individual and social life is outside our present purpose, but they may be briefly summed up as climate, moisture, soil, the configuration of the earth's surface, and the nature of its products. These natural phenomena, either singly or in varying degrees of combination, have unquestionably played a most prominent part in making the different races of mankind what they at present are. We have only to look at the low type of life exhibited by the primitive inhabitants of certain inhospitable regions of the globe to see how profoundly the physical structure of man is affected by his natural surroundings. Even a comparatively slight difference of environment is not without effect upon the population subjected to its influence. According to M. de Quatrefages, the bodily structure of the English race has been distinctly modified by residence in the United States of America. It is not more than two and a half centuries since Englishmen began to emigrate in any considerable numbers to the American Continent, but in that comparatively short period the Anglo-American has ceased to resemble his ancestors in physical appearance. Alterations have taken place in the skin, the hair, the neck, and the head; the lower jaw has become bigger; the bones of the arms and legs have lengthened, and the American of to-day requires a different kind of glove from the Englishman. Structural changes of a similar character have taken place in the negroes transplanted to America. M. Elisee Reclus considers that in a century and a half they have traversed a good quarter of the distance which separates them from the whites. Another important point, as showing the influence of habitat upon race, is the fact that the modifications of human structure resulting from residence in America are in the direction of assimilating the European type to that of the red man.[11] In short, it may be taken as a well-established principle that external nature destroys all organisms that cannot adapt themselves to its action, and physiologically modifies all organisms that can. [11] The various types of Jews also afford a striking instance of the effect of natural surroundings on bodily structure.