CAUSES OF COAGULATION. 43 



ing experiment of Lister : He placed two ligatures on a vein con- 

 taining blood, moistening one-half of the outer surface of the vein 

 with ammonia, and leaving the other half intact. The blood coagu- 

 lated in the first half, and not in the other, owing to the properties of 

 the wall of the vein of the former being altered. Lister also proved 

 that blood will remain fluid for hours in a vein after it has been 

 freely exposed to the air, and even after it has been poured in a thin 

 stream from one vein to another.] Neither the decrease of nor the 

 evolution of ammonia seems to have any causal connection with the 

 formation of fibrin. 



29. Cause of the Coagulation of the Blood, 



Alexander Schmidt stated that fibrin is formed by the coming- 

 together of two proteid substances which occur dissolved in the plasma 

 or liquor sanguinis, viz. : (1.) Fibnnogen, i.e., the substance which yields 

 the chief mass of the fibrin, and (2.) Fibrinoplastic substance or fibrino- 

 plastin. In order to determine the coagulation a ferment seems to be 

 necessary, and this is supplied by (3.) the fibrin-ferment. 



[The serous sacs of the body contain a fluid which in some respects closely 

 resembles lymph. The pericardium contains pericardia! fluid, which in some 

 animals coagulates spontaneously (e.g., in the rabbit, ox, horse, and sheep), if 

 the fluid be removed immediately after death. If this be not done till several 

 hours after death, the fluid does not coagulate spontaneously. The fluid of 

 the tunica vaginalis of the testis, again, sometimes accumulates to a great 

 extent, and constitutes hydrocele, but this fluid shows no tendency to coagulate 

 spontaneously. Andrew Buchanan found, however, that if to the fluid of ascites, 

 to pleuritic fluid, or to hydrocele fluid, there be added clear blood-serum, then 

 coagulation takes place, i.e., two fluids neither of which shows any tendency by 

 itself to coagulate form a clot when they are mixed. He also found that if 

 "washed blood clot" (which consists of a mixture of fibrin and colourless cor- 

 puscles) be added to hydrocele fluid, coagulation occurred. Denis mixed unco- 

 agulated blood with a saturated solution of sodic sulphate, allowed the corpuscles 

 to subside, and decanted the clear fluid which was mixed with sodic chloride, 

 until a large amount of precipitate had been obtained. The precipitate, when 

 washed with a saturated solution of sodic chloride, he called plasmine. If plas- 

 mine be mixed with water, it coagiilates spontaneously, resulting in the formation 

 of fibrin, while another proteid remains in solution. According to the view of 

 Denis, fibrin is produced by the splitting up of plasmine into two bodies fibrin 

 and au insoluble proteid.] 



[Researches Of A. Schmidt- This observer rediscovered the chief facts 

 already known to Buchanan, viz., that some fluids which do not coagulate 

 spontaneously, clot when mixed with other fluids, which also show no tendency 

 to coagulate spontaneously, <:. f j., hydrocele fluid and blood-serum. He proceeded 

 to isolate from these fluids the bodies which are described as fibrinogen and 

 nbrinoplastin. The bodies so obtained were not pure, but Schmidt supposed that 

 the formation of fibrin was due to the interaction of these two proteids. The 

 reason why hydrocele fluid did not coagulate, he said, was that it contained 

 nbrinogeu aiid no fibrinoplaatin, while blood -serum contained the latter, but not 



