306 On the Sense of Feeling. 



mechanically to enable the animal to appreciate the figure and bulk of 

 bodies. 



These parts vary in different animals. In the American monkeys the 

 tail is tiie organ of touch ; and the young of the opossum are known to curl 

 their tails round thatof tiieir mother, and so to steady themselves uj)on her 

 back, while she escapes from the enemy. In all these animals the under 

 surface of the tail, and that only, is naturally deficient in hair, and highly 

 sensible; while in the kangaroo, whose tail, though remarkably large, is 

 not prehensile, tiiere is no difference between one part of it and another ; 

 and in many other animals, possessing large and magnificent tails, there 

 is no remarkable development of tact. 



Bats are remarkable as being able to fly about with perfect facility, 

 either in the dark, or with a very moderate share of liglit ; and it is said, 

 even after their eyes and ears have been destroyed. Some naturalists have 

 claimed for them a sixtli sense, and placed it in their wings. That the 

 wings are well supplied with nerves is true, but there is no necessity for 

 supposing a new sense, since, even if they do fly readily in absolute dark- 

 ness, vvhicli is doubtful, vve might much more easily suppose that a very 

 delicate sense of touch would take cognizance of the returning waves of 

 the atmosphere, just as a blind man becomes aware of the existence of a 

 wall a little before he reaches it. 



In those animals in whom the extremities are used only for locomotion, 

 tlie sense of toucli resides elsewhere : in the elephant it is found in the 

 extremity of his long and flexible proboscis ; in the horse in his full lips ; 

 in the hog in his elongated snout. But of all these, the trunk of the ele- 

 phant is by far the most com])]ete j and, as an organ of attack and defence, 

 of prehension and of touch, is superior to every other of the mechanical 

 contrivances of nature, excepting only the human hand, with the descrip- 

 tion of which organ we will conclude. 



AVlth the general appearance of the human hand we are all familiar. We 

 know that is placed at the extremity of the fore-arm, that it commences 

 from the wrist, that it is divided into a palm, fingers, and a thumb, that 

 the fingers are articulated to the palm by the joints called the knuckles, 

 and that each of them is divided by two joints into three pieces, but that 

 the thumb possesses only two. 



But, duly to appreciate the mechanism of this organ, it is necessary to 

 examine rather more deeply into its substance. AVe shall commence there- 

 fore with its skeleton. 



The hand is composed of twenty-seven bones, which are divided into 

 carpus, metacarpus, and phalanges ; and it is articulated at the wrist with 

 two others, the radius and ulna. 



The carpus consists of eight bones, arranged in two rows. The bony 

 articulations of the wrist joint are carried on between the radius above, and 

 the three upper carpal bones below, the connexion between the ulna 



