64 HANDBOOK OF PHYSIOLOGY. 



fluid does not lack this body, and moreover, if paraglobulin, obtained 

 from serum by the carbonic acid method, be added to it, it will not 

 coagulate, neither will a mixture of solutions of fibrinogen and para- 

 globulin, obtained in the same way. But if paraglobulin, obtained by 

 the saturation method, be added to hydrocele fluid, it will clot, as will 

 also, as we have seen above, a mixed solution of fibrinogen and para- 

 globulin, both obtained by the saturation method. From this it is evi- 

 dent that in plasmine there is something more than the two bodies above 

 mentioned, and that this something is precipitated with the paraglobu- 

 lin by the saturation method, and is not precipitated by the carbonic 

 acid method. 



The following experiments show that it is of the nature of a ferment. 

 If defibrinated blood or serum be kept in a stoppered bottle with its own 

 bulk of alcohol for some weeks, all the proteid matter is precipitated in 

 a coagulated form; if the precipitate be then removed by filtration, 

 dried over sulphuric acid, finely powdered, and then suspended in water, 

 a watery extract may be obtained by further filtration, containing ex- 

 tremely little, if any, proteid matter. Yet a little of this watery ex- 

 tract will produce coagulation in fluids, e.g., hydrocele fluid or diluted 

 plasma, which are not spontaneously coagulable, or which coagulate 

 slowly and with difficulty. It will also cause a mixture of fibrinogen 

 and paraglobulin, both obtained by the carbonic acid method, to clot. 

 The 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 influence 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, appears to belong to that class of 

 bodies which promote the union of, or cause changes in, other bodies, 

 without themselves entering into union or undergoing change, i.e., fer- 

 ments. The third substance 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 some little time afterwards 

 (p. 65). 



So far we have seen that plasmine is a body composed of three sub- 

 stances, viz., fibrinogen, paraglobulin, and fibrin ferment. The next ques- 

 tion which presents itself is, are these three bodies actively concerned in the 

 formation of fibrin f Here we come to a point about which two distinct 

 opinions prevail, and which it will be necessary to mention. 



On the one hand Schmidt holds that fibrin is produced by the inter- 

 action of the two proteid bodies, viz., fibrinogen and paraglobulin, 

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



