THE BT.OOD. " 223 



with minute crranules, which render their outlines more or less ob- 

 scure. 



Once coagulated, fibrine is insoluble in water, and can only be again 

 liquefied by the action of an alkaline or strongly saline solution, by pro- 

 longed boiling at a very high temperature, or by digesting with gastric 

 juice or an acidulated solution of pepsine. These agents, however, pro- 

 duce a permanent alteration in its properties, so that it is no longer the 

 same substance as before. 



The quantity of fibrine obtainable from the blood varies in different 

 parts of the body. According to most observers,* venous blood in 

 general yields less fibrine than arterial blood. In the liver and the 

 kidneys its disappearance is so complete that little or none is to be 

 obtained from the blood of th? renal and hepatic veins. On this 

 account, the blood in the large veins near the heart is more deficient 

 in fibrine than in those at a distance ; since the venous blood com- 

 ing from the general circulation, and containing a moderate quantity, 

 i> mingled, on approaching the heart, with that of the renal and hepatic 

 veins, in which it is nearly or entirely absent. 



A certain quantity of peptone is also found in the plasma, derived 

 from the products of digestion. Its quantity, according to Robin, 

 varies from 1 to 4 parts per thousand. As it is absorbed from the 

 intestine, and neither accumulates in the plasma nor appears in any of 

 the excretions, it is no doubt transformed into some other substance 

 after its entrance into the blood. 



The fatty matters of the blood are in largest quantity soon after the 

 digestion of food rich in oleaginous substances. At that period, the 

 cmulsioned fat finds its way into the blood, and circulates for a time 

 unchanged ; communicating to the serum, when very abundant, a turbid 

 or wliitish appearance. Afterward it gradually disappears from the 

 : ire illation, being either deposited in the fatty tissues or transformed 

 into other products of assimilation. 



The mineral salts of the plasma are principally sodium and potas- 

 sium chlorides, phosphates, and sulphates, together with lime and mag- 

 nesium phosphates. Of these the sodium chloride is the most abundant, 

 constituting nearly 40 per cent, of all the saline ingredients. The 

 sodium and potassium phosphates are important for the alkalescence 

 of the blood-plasma, a property which is essential to the functions of 

 nutrition, and even to the immediate continuance of life ; since it 

 enables the plasma to absorb carbonic acid in the capillary circula- 

 tion, and return it to the lungs for elimination. The alkaline carbon- 

 ates also take part in the production of this alkalescence, and in the 

 herbivorous animals are its principal cause ; while in the carnivora the 

 phosphates are more important in this respect. In man, under an ordi- 

 nary mixed diet, both the phosphates and carbonates are present in 

 varying proportion. 



* Robin, Leyons sur les Humeurs. Paris, 1874, pp. 137, 140, 172. 



