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 



