Traces of Unity, &c. 25 



here the characteristics of the hands are not always 

 lost. The squirrel uses its fore-feet for climbing and 

 holding its food almost as much as the monkey, and the 

 bear and opossum do the same, their case being not very 

 different from that of very many other unguiculate 

 animals : while in the opossum and phalangers the hind 

 foot is more hand-like than the fore-foot, for in them 

 there is, not only a rotatory motion of the hind foot 

 analogous to the pronation and supination of the hand, 

 but also a large great toe which, as in the quadrumana, 

 is fitted for closing strongly upon the other toes like a 

 true thumb an arrangement which (as the fore-foot is 

 less like a hand in that its thumb lies parallel with the 

 fingers) has led to these creatures being called pedimana 

 or foot-handed. 



Nor is there any difficulty in tracing the same com- 

 mon plan in every modification of the hand or foot. 



In plantigrade animals, as in the bear, the whole or 

 nearly the whole of the foot forms a sole : in digita- 

 grade animals, as in the cat or deer, the heel and the cor- 

 responding part in the other foot are much raised and 

 only the tips of the toes rest on the ground. Between 

 quadrupeds with nails, the unguiculata, and quadrupeds 

 with hoofs, the ungulata, there are many points of con- 

 nection. In man and the quadrumana the nails are 

 comparatively insignificant parts : in the cat and dog 

 retractile and non-retractile claws take the place of 

 these simple nails, the chief difference between the two 

 forms of claws being in this, that in the retractile form 

 the terminal phalanx of the toe, to which the claw is 

 attached, is, when it is not drawn down by its flexor 

 tendon in the act of striking or tearing or holding, 

 pulled back over the second phalanx, and so kept out of 

 the way, when the paw is merely used in walking, by the 



