CHAP. II.] THE BLOOD. 53 



as free alkalies or their carbonates, and some salts, will actually exert 

 such an influence. The addition of any body which will combine with, 

 or neutralize, the substances which prevent the separation of fibrin 

 will naturally lead to its formation. If, for example, a hydrocele 

 fluid, which contains but a small quantity of fibrinogen and which 

 will not coagulate on the addition of ferment, be treated with solu- 

 tion of calcium chloride, coagulation will sometimes occur. Now it is 

 conceivable that in this case the chloride acts by decomposing the 

 alkaline carbonate which hinders the precipitation of the fibrin, for 

 were sodium carbonate and calcium chloride to come in contact the 

 reaction would be as follows: Na 2 CO 3 + CaCl^ = 2NaCl + OaGO 3 . 

 Paraglobulin may, perhaps, act in a similar manner, by combining 

 with substances which hinder the precipitation of fibrin. 



Schmidt had discovered that the addition of serum which has 

 been freed from paraglobulin (by dilution with water, passage of CO 2 

 and concentration in vacua) to hydrocele fluid does not cause the 

 latter to coagulate, and Hammarsten confirms the statement in 

 reference to hydrocele fluid or to solutions which are as poor in 

 fibrinogen as that fluid. If, however, such serum, free from para- 

 globulin, be added to a strong solution of fibrinogen, the latter will 

 coagulate well. Hammarsten's explanation is the following : A 

 solution of fibrinogen, prepared according to the method of Schmidt, 

 contains more free alkali than the original fluid did whilst it con- 

 tained paraglobulin. The former contains therefore a larger propor- 

 tion of substances capable of dissolving fibrin, and when it is mixed 

 with a liquid containing only a small quantity of fibrinogen, a larger 

 portion of the resulting fibrin, or it may be the whole of it; may be 

 held in solution. When, however, the same solution is added to 

 a fluid containing an abundance of fibrinogen, the substances capable 

 of dissolving fibrin are no longer capable of holding in solution all the 

 fibrin which is formed ; and in this case coagulation occurs. 



Keviewing all the facts which have been recorded in the preceding 

 pages, it would appear that, on the whole, the evidence is decidedly in 

 favour of the view that the coagulation of the blood is dependent 

 upon the presence in the plasma of a proteid body, fibrinogen, which 

 under favourable circumstances undergoes conversion or perhaps 

 decomposition into fibrin. The conversion of fibrinogen into fibrin 

 outside of the body appears to be connected with the action of a 

 ferment produced in the colourless cells of the blood and probably 

 only set free when these cells break down. 



The influence of salts on coagulation. 



In the course of his researches Schmidt discovered that salts exert a 

 remarkable action in furthering the spontaneous coagulation of liquids 

 containing the various fibrin-factors. 



If from two liquids which yield when mixed a coagulum of fibrin, 

 the salts be separated by dialysis, and the proteids which are precipitated 



