118 MAN AND THE LOWER ANIMALS n 



advantage we must consider with some attention, 

 and compare together, the structure of the human 

 hand and that of the human foot, so that we may 

 have distinct and clear ideas of what constitutes a 

 hand and what a foot. 



The external form of the human hand is familiar 

 enough to every one. It consists of a stout wrist 

 followed by a broad palm, formed of flesh, and 

 tendons, and skin, binding together four bones, 

 and dividing into four long and flexible digits, or 

 fingers, each of which bears on the back of its 

 last joint a broad and flattened nail. The longest 

 cleft between any two digits is rather less than 

 half as long as the hand. From the outer side of 

 the base of the palm a stout digit goes off, having 

 only two joints instead of three ; so short, that it 

 only reaches to a little beyond the middle of the 

 first joint of the finger next it ; and further re- 

 markable by its great mobility, in consequence of 

 which it can be directed outwards, almost at a 

 right angle to the rest. This digit is called the 

 " pollex" or thumb ; and, like the others, it bears 

 a flat nail upon the back of its terminal joint. In 

 consequence of the proportions and mobility of 

 the thumb, it is what is termed " opposable " ; in 

 other words, its extremity can, with the greatest 

 ease, be brought into contact with the extremities 

 of any of the fingers ; a property upon which the 

 possibility of our carrying into effect the concep- 

 tions of the mind so largely depends. 



