SECRETION. 153 



SECRETION. 



The process of secretion consists in the separation of materials 

 from the blood which are either to be again utilized to fulfil some 

 special purpose in the economy, or are to be removed from the 

 body as excrementitious matter ; in the former case they constitute 

 the secretions, in the latter, the excretions. 



The materials which enter into the composition of the secretions 

 are derived from the nutritive principles of the blood, and require 

 special organs e. g., gastric glands, mammary glands, etc. for 

 their proper elaboration. 



The 'materials which compose the excretions preexist in the blood, 

 and are the results of the activities of the nutritive process ; if 

 retained within the body, they exert a deleterious influence upon the 

 composition of the blood. 



Destruction of a secreting gland abolishes the secretion peculiar to 

 it, and it can not be formed by any other gland ; but among the 

 excreting organs there exists a complementary relation, so that if 

 the function of one organ be interfered with, another performs it to a 

 certain extent. 



Classification of the Secretions. 



PERMANENT FLUIDS. 



Serous fluids. Vitreous humor of the eye. 



Synovial fluid. Fluid of the labyrinth of the in- 



Aqueous humor of the eye. ternal ear. 



Cerebro-spinal fluid. 



TRANSITORY FLUIDS. 



Mucus. Pancreatic juice. 



Sebaceous matter. Secretion from Brunner's glands. 



Cerumen (external meatus). Secretion from Lieberkiihn's 



Meibomian fluid. glands. 



Milk and colostrum. Secretions from follicles of the 



Tears. large intestine. 



Saliva. Bile (also an excretion). 



Gastric juice. 



EXCRETIONS. 



Perspiration and the secretion of Urine. 



the axillary glands. Bile (also a secretion). 



