60 AN AMERICA* Til XT-BOOK OF PHYSIOLOGY. 



is a nucleo-proteid, but that this nucleo-proteid is not capable of acting upon 

 fibrinogen until it has combined with the calcium salts of the blood. According 

 to his view, therefore, fibrin ferment, in Schmidt's sense, is a compound of cal- 

 cium and nucleo-proteid. Lilienfeld has shown by chemical reactions that 

 blood-plates and nuclei of leucocytes contain nucleo-proteid material which in 

 all probability is liberated in the blood-plasma by the disintegration of these 

 elements after the blood is shed. Lilienfeld contends, however, that solu- 

 tions of fibrin ferment prepared by Schmidt's method do not contain any 

 nucleo-proteid material, and that, although the liberation of nucleo-proteid 

 material is what starts normal coagulation of blood, nevertheless so-called 

 fibrin ferment is something entirely different from nucleo-proteid. In this 

 point, however, his results are contradicted by the experiments of Pekelhar- 

 ing and of Halliburton, who both find that solutions of fibrin ferment pre- 

 pared by Schmidt's method give distinct evidence of containing nucleo-pro- 

 teid material. We may conclude, therefore, that the essential element of 

 Schmidt's fibrin ferment is a nucleo-proteid compound. The nature of the 

 action of the ferment on fibrinogen is quite undetermined. As was mentioned 

 before, only a portion, and apparently a variable portion, of this fibrinogen 

 appears as fibrin after clotting is completed. Along with the fibrin a new 

 proteid fibrin globulin makes its appearance in the serum. This fact has 

 suggested the view that perhaps the fibrin ferment acts after the manner of 

 the digestive ferments by causing hydrolytic cleavage of the fibrinogen, that 

 is, causes the fibrinogen molecule to take up water and then dissociate into 

 two parts, fibrin and fibrin globulin. Hammarsten, however, is inclined to 

 believe that the reaction is of a different nature, resembling more the change 

 that occurs in the heat coagulation of proteids. According to this suggestion, 

 the ferment causes a molecular rearrangement of the fibrinogen, resulting in 

 the formation of fibrin, most of which is deposited in an insoluble form, while 

 a smaller part, after suffering a still further alteration, appears as fibrin 

 globulin. 



Intravascular Clotting-. — Clotting may be induced within the blood- 

 vessels by the introduction of foreign particles, either solid or gaseous — for 

 example, air — or by injuring the inner coat of the blood-vessels, as in ligat- 

 ing. In the latter case the area injured by the ligature acts as a foreign 

 surface and probably causes the disintegration of a number of corpuscles. 

 The clot in this case is confined at first to the injured area, and is known 

 a- a " thrombus." Intravascular clotting more or less general in occurrence 

 may be produced by injecting into the circulation such substances as leucocytes 

 obtained by macerating lymph-glands, extracts of fibrin ferment, solutions of 

 nucleo-albumins of different kinds, etc. According to the theory of coagu- 

 lation adopted above, injections of these latter substances ought to cause coagu- 

 lation very readily, since the blood already contains fibrinogen, and needs only 

 the presence of ferment to set up coagulation. As a matter of fact, however, 

 intravascular clotting is produced with some difficulty by these methods, show- 

 ing that the body can protect itself within certain limits from an excess of 



