COAGULATION OF BLOOD. 61 



sues which this particular constituent of the blood is destined 

 to nourish ; in the others, it remains and becomes evident as a 

 clot. This explanation is ingenious, but requires some kind of 

 proof before it can be adopted. 



Concerning other theories, as for instance, that coagulation 

 is due to the escape of carbonic acid, or of ammonia, it need 

 only be said that they have been completely disproved. 



We must therefore, for the present, believe that the cause 

 of the coagulation of the blood has yet to be discovered ; but 

 some very interesting observations in connection with the sub- 

 ject have been recently made, and seem not unlikely to lead 

 in time to a solution of this difficult and most vexed question. 

 The observations referred to have been made independently 

 by Alexander Schmidt, although he was forestalled in regard 

 to some of his experiments by Dr. Andrew Buchanan, of Glas- 

 gow, many years ago. 



When blood-serum, or washed blood-clot, is added to the 

 fluid of hydrocele, or any other serous effusion, it speedily 

 causes coagulation, and the production of true fibrin. And 

 this phenomenon occurs also on the admixture of serous effu- 

 sions from different parts of the body, as that of hydrocele with 

 that of ascites, or of either with fluid from the cavity of the 

 pleura. Other substances also, as muscular or nervous tissue, 

 skin, &c., have been found also able to excite coagulation in 

 serous fluids. Thus, fluids which have little or no tendency to 

 coagulate when left to themselves, can be made to produce a 

 clot, apparently identical with the fibrin of blood by the addi- 

 tion to them of matter which, on its part, was not known to 

 have any special relation to fibrin. As may be supposed, the 

 coagulation is not alike in extent under all these circumstances. 

 Thus, although it occurs when apparently-few or no blood-cells 

 exist in either constituent of the mixture, yet the addition of 

 these very much increases the effect, and their presence evi- 

 dently has a very close connection with the process. From the 

 action of the buffy coat of a clot, in causing the appearance of 

 fibrin in serous effusions, it may be inferred that the pale as 

 well as the red corpuscles are influential in coagulation under 

 these circumstances. Blood-crystals are also found to be effec- 

 tive in producing a clot in serous fluids. 



The true explanation of these very curious phenomena is, 

 probably, not fully known ; but Schmidt supposes that in 

 the act of formation of fibrin there occurs the union of two 

 substances, which he terms fibrinoplastin and fibrinogen. 



The substance which he terms fibrmoplastin, and which he 

 has obtained, not only from blood, but from many other liquids 



