64 THE BLOOD. 



covered; but some very interesting observations in con- 

 nexion with the subject 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 ex- 

 periments by Dr. Andrew Buchanan of Glasgow, 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 ad- 

 mixture of serous effusions 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 sub- 

 stances also, as muscular or nervous tissue, skin, etc., 

 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 addition 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 ap- 

 parently 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 evidently has a very close 

 connexion 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 founcl 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 



