138 PRINCIPLES OF PHYSIOLOGY 



Sebaceous matter contains, in addition to 

 water and a very small amount of salts, 

 various fatty acid substances. The sebaceous 

 matter lubricates the surface of the skin. 

 The skin, however, has other important 

 functions. It is not only the organ by which 

 variations of temperature are experienced, 

 but it has to do with the regulation of the 

 temperature of the body. This will be noted 

 in connection with animal heat. It is also 

 the seat of various sensory mechanisms con- 

 nected with the sense of touch. 



71. Matters are also excreted from the 

 body by the bowel. These consist of the 

 refuse materials of food which have never 

 really entered the tissues of the body, and 

 which are therefore not true excretions. 

 Along with these there are bodies derived 

 from the bile, such as pigments, etc., and 

 the secretions of the numerous mucous glands 

 found throughout the whole length of the 

 bowel, and more especially in the great 

 bowel. Little is known of the chemical 

 nature of those matters, nor of the exact 

 origin of the large amount of saline 



