638 THE SENSES 



There is no marked development of common sensibility to be made out 

 in muscles: they may be cut without the production of pain. On the other 

 hand, there is no doubt that afferent impulses must pass upward from muscles 

 and tendons acquainting the brain with their condition. This, then, must be 

 a special sense. It has been suggested that the minute end-bulbs of Golgi 

 found in tendons, and that the Pacinian corpuscles in the neighborhood of 

 joints, are the terminal organs of this special sense. 



Judgment of the Form and Size of Bodies. By the sense of touch the mind 

 is made acquainted with the size, form, and other external characters of 

 bodies. And in order that these characters may be easily ascertained, the 

 sense of touch is especially developed in those parts which can be readily 

 moved over the surface of bodies. Touch, in its more limited sense, or the 

 act of examining a body by the touch, consists merely in a voluntary employ- 

 ment of this sense combined with movement, and stands in the same relation 

 to the sense of touch, or common sensibility, generally, as the act of seeking, 

 following, or examining odors does to the sense of smell. The hand is the 

 best adapted for it, by reason of its peculiarities of structure namely, its 

 capability of pronation and supination, which enables it, by the movement 

 of rotation, to examine the whole circumference of a body; the power it 

 possesses of opposing the thumb to the rest of the hand, and the relative 

 mobility of the fingers; and lastly from the abundance of the sensory terminal 

 organs which it possesses. In forming a conception of the figure and extent 

 of a surface, the mind multiplies the size of the hand or fingers used in the 

 inquiry by the number of times which it is contained in the surface traversed; 

 and, by repeating this process with regard to the different dimensions of a 

 solid body, acquires a notion of its cubical extent, but, of course, only an 

 imperfect notion, as other senses, e.g., the sight, are required to make it 

 complete. 



It is impossible in this consideration to say how much of our knowledge 

 of the thing touched depends upon pressure and how much upon the mus- 

 cular sense. 



II. TASTE AND SMELL. 



The special sense organs for taste and smell are stimulated by chemical 

 substances, the former by chemicals in solution, the latter by volatile materials. 

 They are also closely associated in action and w y e do not always differentiate 

 between the two. 



THE SENSE OF TASTE. 



The conditions for the perceptions of taste are: i, the presence of a sense 

 organ, a nerve, and a nerve center with special endowments; 2, the excitation 

 of the sense organ by the sapid matters, which for this purpose must be in a 

 state of solution; 3, a temperature of about 37 to 40 C. (98 to 100 F.). 



