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Show 446 DARVHNISM CHAP. them. He possessoo the same number of limbs terminating in the same number of digits as belong fundamentally to the mammalian class. His senses are identical with theirs, and his oro-ans of sense arc the same in number and occu.py the same ~elative position. Every detail of structure which is common to the mammalia as a class is found also in man, while he only differs from them in such ways and degrees as tho various species or o-roups of mammals differ from each other. If, then, we ha:e good reason to believe that every existing group of mammalia has descended from some common ancestral form-as we saw to be so completely demonstrated in the case of the horse tribe,-and that each family, each order and even the whole class must similarly have descended from some much more ancient and more generalised type, it would be in the. highe?t degree improbable-:-so improbable a. to be almost mconcmvable-that man, agreemg with them so closely in every detail of his structure, should have had some quite distinct mode of origin. Let us, then, see what other evidence bears upon the question, and whether it is sufficient to convert the probability of his animal origin into a practical certainty. Rudiments and Variations as Indicating the Relation of Man to othe1· Mammals. All the higher animals present rudiments of organs which, thouo-h useless to them, are useful in some allied group, and 0 . are believed to have descended from a common ancestor m which they were useful. Thus there are in ruminants rudiments of incisor teeth which, in some species, never cut through the o-ums; many lizards have external rudimentary leg. ; whileb many birds, as the Apteryx, have quite rudimentary wino-s. Now man possesses similar rudiments, sometimes con~tantly, sometimes only occasionally present, which serve intimately to connect his bodily structure with that of tho lower animals. Many animals, for example, have a special muscle for moving or twitching the skin. In man there arc remnants of this in certain parts of the body, especially in the forehead, enabling us to raise our eyebrows ; but some persons have it in other parts. A few persons are able to move the whole scalp so as to throw off any object placed on the bead, X \' DARWINISM APPLIED '1'0 MAN 447 n.nd this property has been proved, in one case, to be inherited. In tho outer fold of the ear there is sometimes a projecting point, corre ponding in position to the pointed ear of many animals, and believed to he a rudiment of it. In the alimentary canal there is a rudiment-the vermiform appendage of the crecum ·which is noG only u. elc .. , hut is sometimes a cau ·o of disease :uul c1 a,th in man; yet in many vegetable feeding animals it Is very long, and even in the orang-utan it is of considerable length :mel convoluted. So, man possesses rudimentary bones of _a tail concealed beneath the skin, and, in some rare cases, th1s forms a minute extcmal tail. The variability of every part of man's structure is very great, and many of those variations tend to approximate toward::; the structure of other animals. The cour. cs of the ~rtcrics are eminently variable, so that for surgical purpo. es It ha.- been necessary to determine the probable proportion of each variation. The muscles are so variable that in fifty cases the muscles of the foot were found to be not strictly alike in any two, and in some the dovi:Ltions were considerable· while in thirty-six subjects Mr. J. 'Vood observed no fewer th~n 558 muscular variations. Tho same author states that in a sino-le male subject there were no fewer than seven muscuhr variation , all of ·which plainly represented muscles proper to various kinds of apes. The muscles of the bands and arms-parts which arc so eminently characteristic of man-arc extremely liable to vary, so as to resemble the corresponding muscles of the lower animal . That such variations are due to reversion to a former state of existence Mr. Darwin thinks highly probable, and he adds : "It is quite incredible that a man hould, through mere accident, abnormally resemble certain apes in no less than seven of his muscles, if there had been no genetic connection between them. On the other hand, if man is descended from some ape-like creature, no valid reason can he assigned why certain muscles should not suddenly reappear after an interval of many thousand generations, in the same manner as, with horses, asses, and mules, dark coloured stripes suddenly reappear on the legs and shoulders, after an interval of hundreds, or 1nore probably of thousands of generation " 1 1 Descent of Man, pp. 41-43; also pp. 13-15. |
