-THE BLOOD. 261 



view the fact that if a i per cent, solution of potassium oxalate be 

 added to blood in quantity sufficient to precipitate the calcium, coagu- 

 lation will not take place; but if calcium is restored coagulation 

 proceeds in the usual manner. They transfer the sphere of influence 

 of calcium to the formation of the fibrin rather than to the formation 

 of the ferment. 



Pekelharing's researches led him to the conclusion that there 

 arises from the disintegration of the leukocytes a nucleo-proteid, 

 pro-thrombin, which combining with the calcium salt forms the 

 ferment thrombin. This compound then transfers the calcium to 

 the fibrinogen, which in turn becomes fibrin; the latter is therefore 

 a proteid-calcium compound. 



Lilienfeld asserts that fibrin formation is a cleavage process by 

 which fibrinogen is separated into two bodies, one an albumose which 

 remains in solution, the other a proteid to which he has given the 

 name thrombosin. This cleavage is attributed to the action of the 

 usual ferment, a product of the disintegration of leukocytes. Throm- 

 bosin combines, according to Lilienfeld, with calcium to form fibrin. 



In a critical examination of these different theories Hammersten 

 denies that fibrin is a compound of a proteid and calcium ; for chemic 

 analysis of both fibrinogen and fibrin shows that the former contains 

 as much calcium as the latter, and that therefore the view of coagu- 

 lation according to which fibrinogen unites with calcium to form 

 fibrin is without foundation. On the contrary, he maintains that the 

 specific influence of the calcium is directed toward the production of 

 the ferment, for if this be present in sufficient quantity coagulation 

 takes place in a typical manner, no matter whether the blood has 

 been decalcified by potassium oxalate or not. 



Intra- vascular Coagulation. So long as the relations of the 

 blood and the vascular system remain physiologic no coagulation 

 occurs in the vessels ^XThe reason assigned for this is that the fer- 

 ment, though continually being produced, is as rapidly being de- 

 stroyed, and hence never accumulates in amount sufficient to develop 

 fibrin^This view is supported by the fact that if a solution of cell- 

 protoplasm, leukocytes, lymph-corpuscles, etc., presumably contain- 

 ing a large amount of the ferment, be injected into the blood-vessels, 

 extensive intra- vascular coagulation promptly follows^ It is also 

 believed that the lining of the blood-vessel in some unknown way 

 restrains the coagulation process even though the circulation Has 

 come to rest/^ 



Under pathologic conditions of the circulatory apparatus, espe- 

 cially of the internal lining, intra-vascular coagulation frequently 

 arises, though the process can not be considered as identical with 

 extra- vascular coagulation. Many pathologists assert that in its 

 origin, mode of formation, and structure the intra-vascular coagulum 



