THE BLOOD. 65 



when coagulation does not occur in serum, which contains paraglobulin 

 and the fibrin ferment, the non-coagulation is accounted for by lack of 

 fibrinogen. and that when it does not occur in fluids which contain 

 fibrinogen, it is due to the absence of paraglobulin, or of the ferment, or 

 of both. It will be seen that, according to this view, paraglobulin has 

 a very important fibrino-plastic property. 



On the other hand Hammersten holds that paraglobulin is not an 

 essential in coagulation, or at any rate does not take an active part in 

 the process. He believes that paraglobulin possesses the property in 

 common with many other bodies of combining with or decomposing, 

 and so rendering inert certain substances which have the power of pre- 

 venting the formation or precipitation of fibrin, this power of preventing 

 coagulation being well known to belong to the free alkalies, to the alka- 

 line carbonates, and to certain salts ; and he looks upon fibrin as formed 

 from fibrinogen, which is either (1) decomposed into that substance with 

 the production of some other substances ; or (2) bodily converted into it 

 under the action of a ferment, which is frequently precipitated with 

 paraglobulin. 



Hammersten's view as to the formation of fibrin from fibrinogen by 

 the action of a second body, possibly of the ferment class, is now very 

 generally held. The presence of a certain but small amount of salts, 

 especially of sodium chloride, is necessary for coagulation, and without 

 it, clotting cannot take place. 



Sources of the Fibrin Generators. It has been previously re- 

 marked that the colorless corpuscles which are always present in smaller 

 or greater numbers in the plasma, even when this has been freed from 

 colored corpuscles, have an important share in the production of the 

 clot. The proofs of this may be briefly summarized as follows : (1) 

 That all strongly coagulable fluids contain colorless corpuscles almost in 

 direct proportion to their coagulability ; (2) That clots formed on for- 

 eign bodies, such as needles projecting into the interior or lumen of 

 living blood-vessels, are preceded by an aggregation of colorless corpus- 

 cles ; (3) That plasma in which the colorless corpuscles happen to be 

 scanty, clots feebly ; (4) That if horse's blood be kept in the cold, so 

 that the corpuscles subside, it will be found that the lowest stratum, 

 containing chiefly colored corpuscles, will, if removed, clot feebly, as it 

 contains little of the fibrin factors ; whereas the colorless plasma, es- 

 pecially the lower layers of it in which the colorless corpuscles are most 

 numerous, will clot well, but if filtered in the cold will not clot so well, 

 indicating that when filtered nearly free from colorless corpuscles even 

 the plasma does not contain sufficient of all the fibrin factors to produce 

 thorough coagulation ; (5) In a drop of coagulating blood, observed 

 under the microscope, the fibrin fibrils are seen to start from the color- 

 less corpuscles. 

 5 



