70 HAND-BOOK OF PHYSIOLOGY. 



watery extract appears to contain the body which is precipitated with the 

 paraglobulin by the saturation method. Its active properties are entirely 

 destroyed by boiling. The amount of the extract added does not influ- 

 ence the amount of the clot formed, but only the rapidity of clotting, and 

 moreover the active substance contained in the extract evidently does not 

 form part of the clot, as it may be obtained from the serum after blood 

 has clotted. So that the third factor, which is contained in the aqueous- 

 extract of blood, belongs to that class of bodies which promote the union 

 of other bodies, or cause changes in other bodies, without themselves- 

 entering into union or undergoing change, i.e. ferments. The third sub- 

 stance has, therefore, received the name fibrin ferment. This ferment 

 is developed in blood soon after it has been shed, and its amount appears, 

 to increase for a certain time afterward (p. 74). 



The part played by Paraglobulin. So far we have seen that 

 plasmine is a body composed of three substances, viz., fibrinogen, para- 

 globulin, and fibrin ferment. The question presents itself, are these 

 three bodies actively concerned in the formation of fibrin? Here we 

 come to a point about which two distinct opinions prevail, and which it 

 will be necessary to mention. Schmidt holds that fibrin is produced by 

 the interaction of the two proteid bodies, viz., fibrinogen and para- 

 globulin, brought about by the presence of a special fibrin ferment. Also, 

 that when coagulation does not occur in serum, which contains para- 

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

 lack of fibrinogen, and 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. The other opinion, held by 

 Hammersten, is 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 preventing the formation, or precipi- 

 tation of fibrin, this power of preventing coagulation being well known 

 to belong to the free alkalies, to the alkaline 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. 



Influence of Salts on Coagulation. It is believed that the pres- 

 ence of a certain but small amount of salts, especially of sodhini chloride, 

 is necessary for coagulation, and that 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 



