USES OF BLOOD. 97 



of its existence, as such, in the blood in a fluid state, and of 

 its use in the nutrition of certain special textures, and look 

 for the explanation of its functions to those circumstances, 

 whether of health or disease, under which it is produced. 

 In haemorrhage, for example, the formation of fibrin in the 

 clotting of blood, is the means by which, at least for a 

 time, the bleeding is restrained or stopped ; and the material 

 which is produced for the permanent healing of the injured 

 part, contains a coagulable material probably identical, or 

 very nearly so, with the fibrin of clotted blood. 



Fatty Matters. The fatty matters of the blood subserve 

 more than one purpose. For while they are the means, at 

 least in part, by which the fat of the body, so widely dis- 

 tributed in the proper adipose and other textures, is re- 

 plenished, they also, by their union with oxygen, assist in 

 maintaining the temperature of the body. In certain secre- 

 tions also, notably the milk: and bile, fat is an important 

 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 sodium, 

 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 



