148 THE OSTEOLOGY AND JIYOLOGY 



foot, the extensor indicis and extensors of the pollical internodes ; in the opossum, one of 

 the latter is deficient, and the other joins the extensor indicis, forming an extensor of the 

 thumb and forefinger together. Whatever may be said upon the opposite, I have no 

 alternative but to view these combined extensors as homologous with those of the foot just 

 mentioned. 



As will have been gathered from a former part of this memoir, the short palmar muscles 

 of the thumb and little finger are very similar ; and so also, are those of the great and 

 little toe. They appear to consist essentially of a short flexor, an adductoi-, and an abduc- 

 tor in each instance ; either of which, however, may be somewhat modified ; as, for ex- 

 ample, divided into two more or less distinct portions. The curious, oblique short flexor of 

 the great toe, elsewhere particularly described, does not appear to belong to the group with 

 which it is associated, but rather to be a specialized part of the long flexor system. With 

 this exception, there appears to be little diflficulty in homologizing the short palmar and 

 plantar muscles. Bearing in mind the morphology of the digits, the short muscles of the 

 little toe are to be referred to the thenar muscles of the hand, and those of the great toe 

 to the hypotlienar. 



The lumbricales and interossei of hand and foot are obviously homologous. In the case 

 of the former, identification of the individual tendons of the deep and long flexors deter- 

 mines them, each for each. Both sets of interossei are as easily determined, individually, 

 by the correspondences of the digits with which they are in relation. 



The following provisional table exhibits the homologies of the muscles of the fore and 

 hind extremities, according to the identifications that I have endeavored to establish in the 

 present study. However novel any of the correspondences may appear at first glance, it 

 is hoped that they may not be hastily set aside, nor condemned without fair regard to the 

 reasoning by which they have been reached. I should add that Part HE. of the present 

 memoir is merely an abridgement of an argument, originally penned some years since, 

 and which in the interim has appeared in the New York Ifedical Record, as above cited, 

 in its application to the muscles of the human subject ; and that therefore it should be 

 regarded as simply corroborative of the articles in the Record, and examined in connec- 

 tion with the latter. Some additional investigations of lilce character were made in a dis- 

 section of the Ornithorhynchus, and published in the last volume of the Proceedings of the 

 Essex Institute. 



