390 



AX AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



the ventriloquist consists largely in altering the quality of the sounds he pro- 

 duces to imitate the quality they would naturally have if arising under the 

 conditions which he would lead his hearers to believe to be their origin. A 

 comparatively feeble sound near at hand may have the same quality as a loud 

 one heard at a distance ; thus, a frog croaking in an adjoining room was once 

 mistaken by the writer tor a large dog barking outside the building. 



D. Cutaneous and Muscular Sensations. 



General Importance of the Cutaneous and Muscular Sensations. — 

 Cutaneous sensations are aroused by the operation of some form of energy on 

 the skin, and they include the sensation- of touch, of temperature, and of 



pain. By muscular sensation is meant the ap- 

 preciation which we have of the intensity and 

 direction of muscular effort. Closely allied to 

 this sensation is a general sensibility through which 

 we gain a knowledge of the relative position of 

 the parts of our bodies, irrespective of movements. 

 The direction, size, distance, and surface features 

 of external objects are usually made known to us 

 through the sense of sight or of hearing. Yet these 

 fundamental facts regarding the things about us 

 do not become a part of knowledge through direct 

 visual and auditory perception. Such knowledge 

 is based on complex judgments concerning the 

 meaning of auditory and visual phenomena ac- 

 cording as they have, in past experience, been 

 interpreted by tactile and muscular perceptions. 

 That is, when reduced to its simplest terms, out- 

 most practical and important knowledge of the 

 world is the outgrowth of tactile and muscular 

 perceptions ; by and with them all other sense- 

 perceptions of objects have been corrected and compared. Thus, so simple 

 a feat as the estimate of the size of a distant object is the result of 



Fig. 198. —Tactile corpuscle 

 within a papilla of the skin of 

 the hand (from Quain, after Ran- 

 vier) : 71, n, two nerve-fibres pass- 

 ing to the corpuscle; a, a, ter- 

 minal varicose ramifications of 

 the axis-cylinder within the cor- 

 puscle. 



Pig. 191 hematic figure of a neuromuscular spindle of the first type, namely, with complex 



nerve-ending ; adult cat : '•.. capsule ; m. u.h.. motor nerve-bundle ; pi. < -. plate-ending; n. >>-.. nerve-trunk: 

 ,,r. < .. primary ending; s. e., secondary ending ; b. to., axial muscle-fibres. 1 From Rufflni, Journal of l'i<<i*i- 

 ology, vol. xxiii.) 



a complex judgment based on tactile and muscular experience. Through 

 the sense of sight we perceive the ratio of the visual angle subtended by 



