432 PHYSIOLOGICAL CHEMISTRY. 



The white blood-corpuscle consists of a thin envelope filled with an 

 albuminoid (or a mixture of them) called protoplasm. 



The blood-plasma is a colorless liquid of the average composition 

 as follows : 



Per cent. 



Water 90.20 



Albumin 5.30 



Fibrinoplastin 2.20 



Fibrinogen 0.30 



Fatty matters 0.25 



Crystallizable nitrogenous matter 0.40 



Other organic ingredients 0.50 



Mineral salts . . 0.85 



The alkaline reaction of blood is due to the presence of acid sodium 

 carbonate, NaHCO 3 , and sodium phosphate, Na 2 HPO 4 , both of which 

 have a weak alkaline reaction. Besides these alkaline salts, blood 

 also contains others, among them chiefly sodium chloride, and also the 

 chlorides, phosphates, and sulphates of calcium, magnesium, sodium, 

 potassium, etc. 



When blood leaves the body and is allowed to stand a while (or, 

 quicker, on shaking or agitating it violently) it separates into a semi- 

 solid mass termed clot, and a pale-yellow liquid termed serum, which 

 latter, however, also solidifies after a time in consequence of the coag- 

 ulation of the serum-albumin. Clot consists of fibrin, holding in its 

 meshes the blood corpuscles ; the latter may be removed by washing 

 the clot in a stream of water. Another method for obtaining the 

 corpuscles is to dilute mammalian blood with 10 volumes of a 2 per 

 cent, sodium chloride solution, which prevents coagulation, but allows 

 the corpuscles to settle at the bottom of the fluid. 



Fibrin is a proteid, which exists not as such in the blood, but 

 forms whenever the latter is taken from the body (or under some cir- 

 cumstances when within the living body). It is now assumed, that 

 for the formation of fibrin four factors are necessary, viz., fibrino- 

 plastin, fibrinogen, fibrin ferment, and a small portion of neutral 

 salts. The origin of the fibrin ferment is not positively known, but 

 it is supposed to come from the edges of the wounded bloodvessels. 

 The other factors are all present in the blood. How these substances 

 by their interaction produce fibrin is not known ; fibrinogen is the 

 only one of which the total quantity is used. There is always an 

 excess of fibrino-plastin. While the presence of fibrin ferment and 

 neutral salts is necessary, their quantities do not seem to be diminished. 

 The blood corpuscles take no active part in the formation of the clot, 

 but are simply entangled in its meshes. 



