2 6o TEXT-BOOK OF PHYSIOLOGY. 



coagulation is coincident with the appearance of the fibrin, the ante- 

 cedents of this substance, the physical and chemic conditions which 

 condition its development, and the succession of chemic changes in- 

 volved must be determined, before any consistent theory can be 

 established. 



Extra-vascular Coagulation.^At present it is generally be- 

 lieved that the immediate factors concerned in extra- vascular coagu- 

 lation are fibrinogen, a calcium salt T and a ferment-body^ As to the 

 manner in wETch these three bodies react one with another there is a 

 diversity of opinion. At least five different theories are current at 

 the present time, all of which have some features in common, though 

 presenting points of difference. 



Alexander Schmidt long contended that fibrin was the result of 

 a union of fibrinogen and paraglobulin; that the union was brought 

 about by a ferment-body; that the presence of the neutral salts of the 

 plasma was necessary to the activity of the ferment. Previous to his 

 death in 1893 Schmidt modified his view as follows: The insoluble 

 fibrin is developed out of a soluble fibrin derived from paraglobulin, 

 which in turn is a product of general cell disintegration; the conver- 

 sion of the fibrinogen into fibrin is due to the activity of a ferment, 

 thrombin, a derivative of pro-thrombin, a product of the disintegra- 

 tion of leukocytes, lymph-cells, etc.; that the production of thrombin 

 is conditioned by the presence of the neutral salts of the plasma in 

 normal percentages; that no one of these salts, calcium included, acts 

 in a specific manner; finally, that fibrin is not a compound of a pro- 

 teid and calcium. 



Hammersten, as a result of many years of investigation, believes 

 that paraglobulin is not necessary to the process, fibrinogen alone 

 being transformed into fibrin under the influence of the ferment, in the 

 presence of a neutral salt, especially calcium, which acts specifically 

 in a manner different from the sodium salts. Inasmuch as the quan- 

 tity of fibrin produced is always less than the quantity of fibrinogen 

 previously present, Hammersten concludes that the latter substance, 

 under the influence of the ferment, undergoes a cleavage into two 

 unequal portions, one of which remains in solution, the other solidify- 

 ing as fibrin. While admitting that the calcium salts act specifically, 

 he believes that they are concerned rather with the production of the 

 ferment than the fibrin, for if the ferment is present in sufficient 

 quantity coagulation takes place in a typical manner even in the total 

 absence of calcium. 



Arthus and Pages conclude that for the transformation of fibrin- 

 ogen into fibrin the calcium salts are absolutely essential and act in a 

 specific manner; that the ferment causes a cleavage of fibrinogen into 

 two substances, one of which remains in solution, the other com- 

 bines with calcium to form fibrin. They offer in support of this 



