CHAPTER XXI. 



SECRETIONS. 



The secretions which are poured into the alimentary tract 

 have been already described in the chapter on digestion. There 

 are other glands which can now be conveniently considered, 

 since they more or less alter the blood flowing through them, 

 and thus may be said to aid slightly in the perfect elaboration 

 of that fluid. They are, however, subservient to very different 

 functions; some having merely local offices to perform, and 

 others having duties allotted to them of the greatest general 

 importance to the economy. This becomes obvious from a glance 

 at the following enumeration of the remaining glandular organs. 



Secreting glands (other than those forming special digestive 



juices): 



Lachrymal. 

 Mucous. 

 Mammary. 

 Sebaceous. 

 Excreting glands : 



Sudorific. 

 Urinary. 



SURFACE GLANDS. 

 LACHRYMAL GLANDS. 



Most vertebrate animals that live in air have a gland in con- 

 nection with the surface of their eyes, which secretes a thin fluid 

 to moisten the conjunctiva. This fluid commonly passes from 

 the eye into the nasal cavity, and supplies the inspired air with 

 moisture. 



The lachrymal fluid is clear and colorless, with a distinctly 

 salty taste and alkaline reaction. It contains only about 1 per 

 cent, of solids, in which can be detected some albumin, mucus 

 and fat (1 per cent.), epithelium (1 per cent.), as well as sodium 

 chloride and other salts (.8 per cent.). 

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