108 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



We may summarise our present knowledge of the causes of 

 coagulation in the following tabular way : 



From the platelets, 

 and to a lesser degree 

 from the leucocytes, a 

 nucleo-protein is shed 

 out called 



THROMBOGEN. 



From the formed 

 elements of the blood, 

 but also from the tissues 

 over which the escaping 

 blood flows, is shed out 

 an activating agent 

 called 

 THROMBO-KINASE. 



In the blood plasma 

 a protein substance ex- 

 ists called 



FlBRINOGEN. 



In the presence of calcium salts, thrombo- 

 kinase activates thrombogen in such a way that 

 an active ferment is produced, which is called 

 THROMBIN. 



Thrombin or fibrin-ferment acts on fibrinogen in such a way that it is 

 transformed into the insoluble stringy material which is called 

 FIBRIN. 



THE PLASMA AND SERUM 



The liquid in which the corpuscles float may be obtained by 

 employing one or other of the methods already described for pre- 

 venting the blood from coagulating. The corpuscles, being heavy, 

 sink, and the supernatant plasma can then be removed by a pipette 

 or siphon ; the separation can be effected more thoroughly by the 

 use of a centrifugal machine (see fig. 60, Lesson XXI.). 



On counteracting the influence which has prevented the blood from 

 coagulating, the plasma then itself coagulates. Thus plasma obtained 

 by the use of cold, clots on warming gently ; plasma which has been 

 decalcified by the action of a soluble oxalate clots on the addition of 

 a calcium salt ; plasma obtained by the use of a strong solutfon of 

 salt coagulates when this is diluted by the addition of water, the 

 addition of fibrin ferment being necessary in most cases ; where 

 coagulation occurs without the addition of fibrin-ferment, no doubt 

 some is present from the partial disintegration of the corpuscles which 

 has already occurred. Pericardial and hydrocele fluids resemble pure 

 plasma very closely in composition. As a rule, however, they contain 

 few or no white corpuscles, and do not clot spontaneously, but after 

 the addition of fibrin ferment or liquids like serum that contain fibrin 

 ferment they always yield fibrin. 



