68 COAGULATION IS ACCELERATED. 



(/) In cases of bleeders' disease hemophilia coagulation appears to be want- 

 ing on account of deficiency in the fibrin-generators, in consequence of which 

 wounds of the vessels are not occluded by fibrinous thrombi. The peptic ferment 

 of the pancreas dissolved in glycerin and injected into the blood inhibits its coagu- 

 lation, as does also the diastatic ferment. Schmidt-Mulheim noted the same result 

 after injection of pure peptone into the blood of dogs 0.5 gram to i kilo of dog, 

 and 1.5 of rabbit. This is effective, however, only in the presence of the liver. 

 The buccal secretion of the leech, the poison of vipers and the highly toxic substance 

 in the serum of eels' blood likewise inhibit coagulation. 



Coagulation is accelerated: 



(a) By contact with foreign substances to which the blood adheres, 

 as, for instance, threads and needles introduced into the veins. Also 

 the entrance of air-bubbles into the vessels or the passage of other 

 indifferent gases, as, for instance, nitrogen and hydrogen, exerts an 

 accelerating effect. Removed from the vein, the blood coagulates 

 quickly on the walls of the container, on its surface exposed to the air, 

 on the rod with jvhich it is whipped, etc. 



(6) Many products of the retrogressive metamorphosis of albuminates, 

 including uric acid, glycin, taurin, leucin, tyrosin, guanin, xanthin, 

 hypoxanthin (not urea), as well as the biliary acids, further lecithin, 

 cholin hydrochlorate, protagon, accelerate coagulation through in- 

 creased ferment-formation. Added in excess, however, they exert an 

 inhibiting effect. Solutions of gelatin injected into the veins cause the 

 blood to coagulate almost instantly after escape from the vessels. 



(c) If hemorrhage takes place rapidly the last amounts of blood 

 coagulate earliest. Fresh fibrin, if permitted to remain for a consider- 

 able time in blood, is again dissolved in part. 



(d) Heating to a temperature of from 39 to 55 C. accelerates 

 coagulation. 



In the shed blood of man coagulation begins in the course of three 

 minutes and forty-five seconds; in that of woman after two minutes 

 and thirty seconds. Hunger exerts an accelerating effect. 



Among vertebrates the blood of birds coagulates almost instantly, that of 

 cold-blooded animals distinctly more slowly, while the blood of mammals occupies 

 an intermediate position. The blood of invertebrates, which mostly is colorless, 

 forms a soft, white fibrinous coagulum. 



As the process of coagulation involves a change in the aggregate 

 state, heat demonstrable with the thermometer must be set free. 



In blood removed from a vein the degree of alkalinity diminishes 

 up to the point of completed coagulation, probably from the formation 

 of acid in the blood as a result of decomposition-processes. 



In the process of coagulation a diminution in the amount of oxygen in the 

 blood has been observed, although this takes place also in blood that has not yet 

 undergone coagulation. There is, likewise, elimination of traces of ammonia. 

 Both processes, however, appear not to stand in causal relation with the formation 

 of fibrin. 



NATURE OF COAGULATION. 



Alexander Schmidt discovered in 1861 that coagulation is a fermen- 

 tative process that consists in the transformation of the soluble albumin 

 of the plasma into the solid substances of the fibrin through the activity 

 of an enzyme that is designated fibrin-ferment or thrombin. This pro- 

 teid is nothing but fibrinogen. 



