Wilder.] 334 [June 21, 



acknowledge that the " law which causes the modifications of organ- 

 isms, becomes more and more decided and clear from tlie centre to the 

 "perifjhery" I may here say that the convictions expressed in 58, 

 (Props. 9 and 10) were formed independently of the authors above 

 quoted. 



The results of a tabulation of cases of sexdigitism and hexadactyl- 

 isni, 1 (as given in 313), have been»confirniedby the addition of cases, 

 gathered up to Jan. 1, 1870 ; at that date, of 242 individuals affected^ 

 152 were males and 90 females; and of the membra, 312 were arnii 

 and only 155 skelea ; this not only shows the extreme frequency of 

 this malformation of peripheral parts belonging to the highest verte- 

 brate animal, but also indicates that in this respect, the skelos is 

 more constant and reliable than the annus, as it is also the membrum 

 less often and less extensively modified for special purposes through- 

 out the vertebrate type (313, 10) ; but in respect to the vascular 

 system, particularly, Meckel believes the reverse is the case, (6, 

 English edition, 2, 176) ; and upon this question more remains to be 

 done. 



Another very important question is as yet undecided ; is the ho- 

 mology of a muscle to be determined mainly by its place of origin, or 

 its point of insertion ? The latter is the opinion of Mivart (46, 398) 

 Rolleston (61, 620), (with some exceptions), and Humphrey (64, 

 321). Coues states that the insertion is less frequently changed than 

 the origin (70, 223), and I know of no author who has taken the op- 

 posite view 2 ; I am not now prepared to do so, and would suggest that 

 we ought first to discriminate between the " sliding up or down the 

 same bone" referred to by Coues (70, 223), and the lateral transfer 

 from one bone to another, as of the tendon of insertion of the biceps 

 brachiaUs (Coues, 70, 299) ; the former transfer would generally be 

 for the purpose of securing greater length of fibre, and extent of mo- 

 tion, and would also occur more frequently with the origin ; but the 

 latter would affect the essential function of the muscle, and would 

 perhaps warrant us in regarding a muscle so affected as wholly dis- 

 tinct. 



1 Do cases ever occur of extra digits, or dactyls upon both borders of the manus 

 or pes? 



2 Since this was written, the graduation thesis of W. S. Barnard, "On the Mem- 

 bral Myology of the Orang" has been prepared in my laboratory, and the facts and 

 ideas therein presented have nearly convinced me that the homology of muscles 

 depends far more upon their origins than upon their insertion : the paper has been 

 offered for publication to the Boston Society of Natural History. 



