62 HANDBOOK OF PHYSIOLOGY. 



of all at the circumference of the containing vessels, and gradually ex- 

 tending throughout the mass. 



If a further portion of plasma be whipped with a. bundle of twigs, the 

 fibrin may be obtained as a solid, stringy mass, just in the same way as 

 from the entire blood, and the resulting fluid no longer retains its power 

 of spontaneous coagulability. 



In these experiments, it is not necessary that the plasma shall have 

 been obtained by the process of cooling above described, as plasma 

 obtained in any other way. e. #., by allowing blood to flow direct from 

 the vessels of an animal into a vessel containing a third or a fourth of 

 its bulk of a saturated solution of a neutral salt (preferably of magne- 

 sium sulphate) and mixing carefully, will answer the purpose and, just 

 as in the other case, the colored corpuscles will subside leaving the clear 

 superstratum of (salted) plasma. In order that this plasma may coagu- 

 late, it is necessary to get rid of the salts by dialysis, or to dilute it with 

 several times its bulk of water. 



Evidently, therefore, fibrin is as a rule derived from the plasma of 

 blood 



The second step in the investigation is to consider from what part of 

 the plasma fibrin is formed, and to that we shall now turn our attention. 



If plasma be saturated with solid magnesium sulphate or sodium 

 chloride, a white, sticky precipitate called plasmine is thrown down, 

 after the removal of which, by filtration, the plasma will not spontane- 

 ously coagulate. Plasmine is soluble in dilute neutral saline solutions, 

 and the solution of it speedily coagulates, producing a clot composed of 

 fibrin. Blood plasma therefore contains a substance without which it 

 cannot coagulate, and a solution of which is spontaneously coagulable. 

 This substance is very soluble in dilute saline solutions, and is not, 

 therefore, fibrin, which is insoluble in these fluids. We are, therefore, 

 led to the belief that plasmine produces or is converted into fibrin, when 

 clotting of fluids containing it takes place. 



There is distinct evidence that plasmine is a compound body made 

 up of two or more substances, and that it is not mere soluble fibrin. 

 This view is based upon the following observations: There exists in all 

 the serous cavities of the body in health, e. g., the pericardium, the 

 peritoneum, and the pleura, a certain small amount of transparent fluid, 

 generally of a pale straw color, which in diseased conditions may be 

 greatly increased. It somewhat resembles serum in appearance, but in 

 reality differs from it, and is probably closely allied to plasma. This 

 serous fluid is not, as a rule, spontaneously coagulable, but may be made 

 to clot on the addition of serum, which is also a fluid which has no ten- 

 dency of itself to coagulate. The clot produced consists of fibrin, and 

 the clotting is identical with the clotting of plasma. From the serous 

 fluid (that from the inflamed tunica vaginalis testis or hydrocele fluid is 



