LECTURE III. 13$ 



exerted by the whole of the fingers and 

 hand, in grasping. The second joint of 

 the thumb resembles the first joint of the 

 fingers, not only in the form of the bones, 

 but also in the arrangement of the liga- 

 ments, which limit the motions nearly to 

 those of/ a hinge, and the last joint of the 

 thumb, is like either of the two last joints of 

 the fingers, a perfect hinge. 



The fingers and thumb are of unequal 

 length, and, on this account, they are pe- 

 culiarly adapted for grasping spherical bo- 

 dies, which are most difficult to seize and 

 to hold. If, for instance, we take hold of 

 a pocket globe, placing one of its poles in 

 the hollow of our hand, we find all our 

 fingers and the thumb opposing each other 

 upon some parallel of latitude, and thus 

 giving the greatest security to our grasp. 



When the elbow-joint is fixed, the hand 

 describes a complete semicircle, in prona- 

 tion and supination ; and the extent of its 

 motion, in these directions, may be in- 

 creased by variations in the position of the 



K 3 



