40 A MANUAL OF PHYSIOLOGY 



fibrin -ferment is present in it, because the fibrinogen has all 

 been changed into fibrin during coagulation of the blood, 

 can be made to coagulate by the addition of hydrocele fluid, 

 which contains fibrinogen. We have thus arrived a step 

 farther in our attempt to explain the coagulation of the 

 blood : it 'is essentially due to the formation of fibrin from the 

 fibrinogen of the plasma under the influence of fibrin- ferment. 



What is the nature of the fibrin-ferment, and what is its 

 source ? There seems good reason for believing that it 

 has very close relations with a substance or substances 

 belonging to the group of nucleo-proteids, for nucleo-proteid 

 can be obtained from solutions of fibrin-ferment, and, by 

 appropriate treatment and in the presence of proper con- 

 ditions, solutions of nucleo-proteid can either be made to 

 yield fibrin-ferment or to develop that influence on coagula- 

 tion which is the characteristic test by which we recognise 

 it. Nucleo-proteids are contained in the nuclei and proto- 

 plasm of cells, and have been prepared from the thymus, 

 testis, kidney, lymphatic glands, and other organs, by pre- 

 cipitating their watery extracts with dilute acetic acid 

 (Wooldridge), or by extracting with sodium chloride and 

 then precipitating with excess of water (Halliburton). The 

 precipitated nucleo - proteid can be dissolved in dilute 

 sodium carbonate solution. When it is injected slowly or 

 in small amount into the veins of an animal, it abolishes for 

 a time the power of coagulation of the blood ; and when this 

 ' negative phase/ as it is called, has been once established, 

 even a very large and rapid injection produces no further 

 effect. If, however, a considerable quantity of the solution has, 

 been injected at the first, the result is very different : exten- 

 sive intravascular clotting instantly ensues ; the animal dies 

 in a few minutes ; and the right side of the heart, the venae 

 cavse, the portal vein, and perhaps the pulmonary arteries, 

 may be found choked with thrombi. Curiously enough, no 

 such effects are produced in albino rabbits or in Norway hares 

 in their albino condition (Pickering). A solution of fibrin- 

 ferment prepared by Schmidt's method behaves, when in- 

 jected into the blood-stream, like a weak solution of nucleo- 

 proteid, readily producing the negative phase, but causing 



