PRESENT I'KMir.l.KMS IN HVoLUTION AND IlKi; 1 ;i )ri'V. ,'Ul 



iiilH'ritanco would lu^ ;iii actual evil : "J^)()n('S would oltcii he iiiodilied 

 disastrously. Thus the c.oudyh' of the human jaw would becoMic 

 lai <i'er than tlie body <>1" the Jaw. because as tlie iuleiuin of the le\-er 

 it receives more ])ressure. Some oriiaiis (like tiie heart, which is 

 always at work) wouhl l)ccomc inconveniently or unnecessarily large. 

 Other absolutely indispensable organs which are eomi)aratively pas- 

 sive or are very sehlom used would dwindle until their weakness 

 caused the ruin of the individual or the extinction of the species." 

 lie later cites from ])arwin* tlie " Kepoi't of the ITuited States dom- 

 ndssioii upon the Soldiers and Sailors of the Late War." that the 

 loniicr leiis aiul shorter arms of the sailors are the reverse of what 

 should result from the decreased use of the legs in walking and 

 increased use of the arms in pulling. A little retieetiou on Mr. IJalTs 

 ])art would have spared us this crude objection, for whatever dititicul- 

 tics may arise from theoretical si)eeTdation as to the laws of growth, 

 or fiom statistics, the fact remains that activity nnist increase ada])ta- 

 tion in every part of the organism; otherwise the runner and the 

 trotting horse should be kept off the track to increase their speed, 

 the i)ianist should employ as little linger exercise as possibles If the 

 grow'th tendencies in single organs are transmitted, it is evident that 

 the adaptive adjustments between these tendencies will also be trans- 

 nutted. 



The T\M't. — In point of meehani<'al ada])tation, man, with the single 

 excei)tion of his thumb and forearm, has not progressed beyond the 

 most i)rimitive eocene rpiadrnped. The laws of evolution of the foot 

 in the ungulate or hoofed animals, which have been especially studied 

 l)y Kowalevsky, liyder, Cope, and myself, affords a conclusive dem- 

 onstration that the skeletal changes in the individual coincide with 

 those which will mark the evolution of the race. In the <>arliest un- 

 gulates the carpals and tarsals are disposed, as in man, directly above 

 each other, with serial joints, as in diagram .1, Fig. 2; in the course 

 of e\-olutioii all these joints became interlocking, as in diagram B, 

 Fig. .■>; thus producing an alternation of joints and surfacjes sinnlar to 

 those which gi\-e str(;ngth to masonry. In studying these facts Coi)et 

 icaciied a certain theory as to the motion of the foot and leg in loco- 

 motion. In trying to apply this, T found it could not be harmonized 

 with all the facts, and 1 w^trked out an entirely different theory.t This 

 I found subsequently coincided exactly with the results ])reviously 

 <»btained b> ^luybridge, by the aid of instantaneous i)hotograplis, and 

 summarized by Prof. Harrison Allen, of the Uni\ersity oi" Tennsyl- 

 vania.§ 



The monodactylism of the horse was attained by the atrophy of the 



' Descent of Man, p. 32. 



t A )n cried II Natiiralixi, 18S7, p. !»8tJ. 



t S<'o Tiunix. (if Amer'icau I'hUosophicdl Socielii. 1889, ]!. 561. Pliiliiilol|)lii;i. 



^'Vhe Muybridge Work tit tlic University of Peuiisylvauia. J'iiiladelpliia, 1888. 



