106 USES OF BLOOD. 



of the Blood. 



The purposes of the blood, thus developed and main- 

 tained, appear, in the perfect state, to be these ; ist, 

 to be a source whence the various parts of the body may 

 abstract the materials necessary for their nutrition and 

 maintenance ; and whence the secreting organs may take 

 the materials for their various secretions ; 2nd, to be an 

 ever constantly replenished store-house of latent chemical 

 force, which in its expenditure will maintain the heat of 

 the body, or be transformed by the living tissues, and 

 manifested by them in various forms as vital power ; $rd, 

 to convey oxygen to the several tissues which may need it, 

 either for. the discharge of their functions, or for combination 

 with their refuse matter ; 4^, to bring from all parts refuse 

 matters, and convey them to places whence they may be dis- 

 charged ; 5^, to warm and moisten all parts of the body. 



Uses of the various Constituents of the Blood. 

 Eegarding the uses of the various constituents of the 

 blood it may be said that the matter almost resolves itself 

 into an analysis of the different parts of the body, and of 

 the food and drink which are taken for their nutrition, 

 with a subsequent consideration of how far any given con- 

 stituent of the blood may be supposed to be on its way 

 to the living tissues, to be incorporated with and nourish 

 them, or, having fulfilled its purpose, to be on its way in a 

 more or less changed condition to the excretory organs to be 

 cast out. It must be remembered, however, that the blood 

 contains also matters which serve by their combustion 

 to produce heat, and, again, others which possibly sub- 

 serve only a mechanical, although most important, purpose ; 

 as for instance the preservation of the due specific gravity 

 of the blood, or some other quality by which it is enabled 

 to maintain its proper relation to the vessels containing it 

 and to the tissues through which it passes. Lastly, among 

 the constituents of the blood, are the gases, as oxygen and 

 carbonic acid, and the substances specially adapted to carry 



