CHAP, i.] 



BLOOD. 



17 



serum. Now the addition of serum will often bring about coagu- 

 lation in fluids which, left to themselves, will not coagulate, the 

 clot so formed being composed of fibrin with normal characters, and 

 the artificial coagulation thus induced being in all other respects 

 exactly like a natural clotting. Thus for instance bydrocele fluid, 

 carefully removed without admixture of blood from a hydrocele, 

 will in most cases remain fluid without any disposition to clot 1 . 

 So also the serous fluid removed from the pericardial, pleural, or 

 peritoneal cavities some hours after death in most cases shews no 

 disposition to clot 2 . But these fluids, hydrocele or pericardial, 

 though they do not clot spontaneously, will generally, upon the 

 addition of serum or a little whipped blood, clot in a most unmis- 

 takeable manner 3 . Now fibrinogen is certainly present in these 

 fluids, and may be thrown down from them by the addition of 

 sodium chloride or by other means ; and, since serum contains 

 paraglobulin, it was at first thought that the absence of spontaneous 

 coagulation in the untouched hydrocele or pericardial fluid was 

 due to the absence of paraglobulin, which as we have seen is 

 present with fibrinogen in the spontaneously coagulable plasma of 

 blood, and that the coagulating effect of the addition of the serum 

 was due to the paraglobulin it contained, the paraglobulin and 

 fibrinogen acting in some way or other upon each other to produce 

 fibrin. And this view was supported by the fact that paraglobulin 

 precipitated from serum was, like the entire serum, efficacious in 

 giving rise to a coagulation in fibrinogenous pericardial, or hydrocele 

 fluids. 



It was soon found however that certain specimens of pericardial 

 and even hydrocele fluid did not need the addition of the para- 

 globulin to make them coagulate; that though they would not 

 coagulate spontaneously they might be made to coagulate by 

 adding to them a constituent of serum which was not paraglobulin 

 but something else. Thus if serum, or indeed whipped blood, be 

 mixed with a large quantity of alcohol and allowed to stand some 

 days, the proteids present are in time so changed by. the alcohol 

 as to become insoluble in water. Hence if the copious precipitate, 

 after long standing, be separated by filtration from the alcohol^ 

 dried at a low temperature not exceeding 40, and extracted with' 

 distilled water, the aqueous extract contains very little proteid 

 matter, indeed very little organic matter at all. Nevertheless 

 even a small quantity of this aqueous extract added alone to certain 

 specimens of hydrocele fluid will bring about a speedy coagulation. 

 The same aqueous extract has also a remarkable effect in hastening 

 the coagulation of fluids which though they will eventually clot, 

 do so very slowly. Thus plasma may, by the careful addition of a 



1 In some specimens, however, a spontaneous coagulation, generally slight, but 

 in exceptional cases massive, may be observed. 



2 If it be removed immediately after death it generally clots readily and firmly, 

 giving a colourless clot consisting of fibrin and white corpuscles only. 



3 In a few cases no coagulation can thus be induced. 



F. 2 





/T 



