464 THE ASCENT OF MAN. 



anthropoid apes. The i)harynx of the embryo is lined with cilia like that 

 of the very lowest vertebrates. Traces of the i)riiuitive intestine are 

 shown by the peculiar distribution of nerve.s and the foldinj;^ of the 

 peritoneum. The liver and spleen both occasionally indicate a previous 

 simpler condition, and the intestine has sometimes diverticula of no 

 functional use — indeed, likely to be disadvantageous — yet i)ointing to 

 a i)revious state. These anomalies never occur at random, but can be 

 explained consistently upon the theory of reversion. 



The genito-urinary system abounds in them. The uterus may have 

 two cavities, as in many quadrupeds, or ai)proach that condition by 

 being bicornuate, as in apes, and a great variety of other vestigial 

 structures occur, all pointing back to an original neutral condition, 

 before the sexes were ditifereutiated. 



In the nervous system there is no lack of instances. Our studies of 

 the brain are as yet far from complete — indeed, we seem to be only at 

 the threshold of a reasonable knowledge of the nervous centers — and 

 the crowd of names, the inextricable maze of synonymy that now ob- 

 scures that region, is only a mark of our ignorance. It is a case of 

 '''■omne ignotum pro mirijico;^'' ignorant of the true value of the parts 

 we examine, we have named even the most insignificant details of struc- 

 ture. Perhaps one of the most interesting results of modern research 

 is the conclusion that the psychic life of our ancestors must have been 

 difterent from our own, since they possessed organs of sensation differing 

 in degree and i)r()bably in kind. The sense of smell as indicated by the 

 size of the olfactory bulbs of the brain is decreasing in acuteness. The 

 foetal brain possesses comparatively larger bulbs, as do also the brains 

 of lower races, and of anthropoid apes. The sense, being no longer re- 

 quired for the preservation of the si)ecies, is slowly becoming dulled. 

 Jacobsou's organ, a curious structure found in many mammals, com- 

 biuing in some unknown manner the olfactory and gustatory senses, 

 occurs in a vestigial state in man, and the duct connecting it with the 

 mouth yet remains as the anterior palatine canal. The pineal and pitu- 

 itary bodies of the brain probably rei)resent obliterated sense organs, 

 the former being an eye, the latter having some connection with the 

 pharynx. Our other senses have also been modified. The eye has a 

 rudimentary third eyelid, such as birds and lizards possess, covered 

 with minute hairs. The external ear shows signs of derivation from the 

 pointed ear of (piadrupeds and abounds in vestigial muscles such as 

 they use for controlling and directing it. 



FrOm this rapid sketch it will be ap[)arent to you that the evidence 

 that man's i)ath upward has led along the same route travelled l)y other 

 animals is now very powerful in its cumulative weight. i>y no other 

 argument can we satisfactorily explain the bewildering maze of resem- 

 blances; yet when called upon to fix the exact line by which weli:ive 

 reached our present estate we at once meet with serious difficulties. 

 It is a i)Oi)ular miscouception that then; has been a regular chain like 



