THE CIRCULATING LIQUIDS OF THE UODY 43 



for a time of its power of coagulation, apparently in part by 

 reason of the affinity of peptone for calcium salts, for its 

 action can be prevented by injection of calcium chloride 

 (Pekelharing), and imitated by injection of potassium oxalate, 

 while the peptone plasma outside of the body can sometimes, 

 though not invariably, be caused to clot by the addition of 

 a soluble salt of calcium. (But see p. 45.) Soaps hinder 

 coagulation in the same way. The precise action of the 

 calcium has not yet been made clear. Pekelharing supposes 

 that active fibrin-ferment is a compound of calcium with 

 nucleo-proteid, and that in coagulation calcium is handed 

 over to the fibrinogen by the fibrin-ferment. Lilienfeld 

 imagines that the nucleo-proteid first acts on the fibrinogen, 

 causing it to split up into thrombosin and fiDrinoglobulin, 

 and that the thrombosin then unites with calcium to form 

 fibrin. To sum up, we may say that there is a general agreement 

 that the presence of calcium is essential to the formation of fibrin, 

 and a preponderance of opinion that the fibrin is formed by the 

 union of calcium with fibrinogen (or thrombosin} under the 

 influence of fibrin-ferment (or nucleo-proteid). 



To a certain extent the action of nucleo-proteid in coagulation can 

 be imitated by other substances of animal origin, such as the 

 albumoses of snake venom (Martin), and even by certain artificial 

 products of the laboratory, the synthesized colloids of Grimaux, 

 which, when injected into the blood, produce the same phenomena 

 of intravascular coagulation down to the finest detail, and including 

 the negative phase. It is not known whether these substances act 

 on the leucocytes or other cells, and thus cause an increased pro- 

 duction or an increased liberation of nucleo-proteid, or whether they 

 actually take its place. 



So far we have been considering the problem of coagulation as if 

 all the data for its solution could be obtained by a study of the blood 

 itself. In other words, our main business up to this point has been 

 the explanation of coagulation in the shed blood ; it has been only 

 incidentally, and with the object of casting light on the question of 

 extravascular clotting, that we have touched on the coagulation of 

 the blood within the living vessels. It is not possible here to 

 adequately discuss, nor even to define, the differences between the 

 two problems. All we can do is to warn the student, and to 

 emphasize our warning by one or two illustrations, that valuable as is 

 the knowledge derived from experiments on extravascular coagula- 

 tion, it would be totally misleading if applied without modification 

 to the circulating blood. For instance, we have recognised in the 

 leucocytes an important source of the nucleo-proteid which plays so 



