io8 USES OF BLOOD. 



replenished, they also, by their union with oxygen, assist 

 in maintaining the temperature of the body. In certain 

 secretions also, notably the milk and bile, fat is an impor- 

 tant constituent. 



Saline Matter. The uses of the saline constituents of 

 the blood are, first, to enter into the composition of such 

 textures and secretions as naturally contain them, and, 

 secondly, to assist in preserving the due specific gravity 

 and alkalinity of the blood and, perhaps, also in preventing 

 its decomposition. The phosphate and carbonate of soda, 

 besides maintaining the alkalinity of the blood, are said 

 especially to preserve the liquidity of its albumen, and to 

 favour its circulation through the capillaries, at the same 

 time that they increase the absorptive power of the serum 

 for gases. But although, from the constant presence of a 

 certain quantity of saline matter in the blood, we may 

 believe that it has these last-mentioned important functions 

 in connection with the blood itself, apart from the nutri- 

 tion of the body, yet, from the amount which is daily 

 separated by the different excretory organs, and especially 

 by the kidneys, we must also believe that a considerable 

 quantity simply passes through the blood, both from the 

 food and from the tissues, as a temporary and useless 

 constituent, to be excreted when opportunity offers. 



Corpuscles. The uses of the red corpuscles are probably 

 not yet fully known, but they may be inferred, at least in 

 part, from the composition and properties of their contents. 

 The affinity of cruorin for oxygen has been already men- 

 tioned ; and the main function of the red corpuscles seems 

 to be the absorption of oxygen in the lungs by means of 

 this constituent, and its conveyance to all parts of the body, 

 especially to those tissues, the nervous and muscular, the 

 discharge of whose functions depends in so great a degree 

 upon a rapid and full supply of this element. The readi- 

 ness with which cruorin absorbs oxygen, and delivers it up 

 again to a reducing agent, so well shewn by the experi- 

 ments of Prof. Stokes, admirably adapts it for this purpose. 



