i367,] 275 [Wyman. 



Miking use of this principle, we shall have the following bones in 

 the two limbs homologous ; beginning on the inside : — 



HAND. FOOT. 



Pisiform 



Pyramidale Scaphoid. 



Lunare Os calcis. 



Scaphoid Astragalus. 



Uneiform 1st cuneiform. 



Magnum 2d cuneiform. 



Trapezoid 3d cuneiform. 



Trapezium Cuboid. 



When applied to the human hand and foot with their high degree 

 of specialization, this mode of comparison seems at first sight inadmis- 

 sible, but bearing in mind the fact that the type is much more distinctly- 

 indicated in the lower, than the higher members of a series, and 

 beginning our comparisons in the lowest, the difficulties growing out 

 of the special developments are obviated. It will be found that in 

 reptiles the tarsus, for the most part, articulates with the leg by two, 

 and even three, bones instead of by one, as in ordinary mammalia; 

 that the astragalus and os calcis neither of them have the peculiar 

 characters which are exhibited in the higher vertebrates, while in the 

 seals among mammals the astragalus develops a. tuberosity backwards 

 equal to that of the os calcis of the same animal. 



We have placed no bone opposite the pisiform as its homologue. 

 Some homologists, and among them Owen, regard the os calcis as, in 

 itself, repeating the pisiform and pyramidale, and as consisting really 

 of two bones combined in one, as the scaphoid and lunare are in the 

 carpus of the cat and some other mammals. This view does not seem 

 to be well supported ; for while the coalescence of the scaphoid and 

 lunare in various animals is a matter of observation, the existence of 

 an OS calcis in two parts has not been observed in any. In its mode 

 of ossification, except in the development of a thin scale on the end 

 of its tuberosity, it follows that of the other tarsal bones, viz., from a 

 single centre. And in having an epiphysis it agrees with the astragalus 

 in some lower animals, as the seal. The relation of the pisiform to 

 the tendon of the " ulnar flexor " (extensor) of the wrist seems to 

 justify Cruvellhier's view that it belongs to the category of sesamoids. 



The metacarpal and metatarsal bones offer no difficulty in either of 

 the two methods of studying the skeleton, since they agree in their 

 relative position, and the only differences are purely teleologlcal ones. 

 Excepting in the thumb and great toe the same may be said of the 

 phalanges. We have already alluded to the great difficulty which the. 

 exceptions just mentioned offer when the limbs are studied as symmet 



