86 USES OF THE BLOOD. 



portant 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 con- 

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

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

 carbonic acid, and the substances specially adapted to carry 

 them, which can scarcely be aid to take part in the nutrition 

 of the body, but are rather the means and evidence of the 

 combustion before referred to, on which, to a great extent, 

 directly or indirectly, all vitality depends. 



Albumen. The albumen, which exists in so large a propor- 

 tion among the chief constituents of the blood, is without 

 doubt mainly for the nourishment of those textures which 

 contain it or other compounds nearly allied to it. Besides its 

 purpose in nutrition, the albumen of the liquor sanguinis is 

 doubtless of importance also in the maintenance of those essen- 

 tial physical properties of the blood to which reference has 

 been already made. 



Fibrin. It has been mentioned in a previous part of this 

 chapter, that the idea of fibrin existing in the blood, as fibrin, 

 is probably founded in error ; and that it is formed, in the act 

 of coagulation, by the union of two substances, which before 

 existed separately (p. 61). In considering, therefore, the func- 

 tions of fibrin, we may exclude the notion of its existence, as 

 such, in the blood, in a fluid state, and of its use in the nutri- 

 tion 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 hemorrhage, for ex- 

 ample, 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 per- 

 manent healing of the injured part, contains a coagulable ma- 

 terial 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 distributed in the 

 proper adipose and other textures, is 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 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. 



