COAGULATION. 469 



0.3 gm. to each kilogram of animal the coagulability of the blood is 

 very greatly diminished for a brief period of half an hour or more. 

 When, however, such solutions are added to freshly drawn blood 

 they exercise no influence upon the coagulation. Evidently, 

 therefore, when injected into the blood they provoke a reaction of 

 some sort, the products of which prevent coagulation. There is 

 evidence to show that this reaction takes place in the liver, and in 

 accordance with this view it is found that much smaller quantities 

 of the peptone solution suffice to give a delayed coagulation when 

 injected directly into the ,. portal vein. As stated in the pre- 

 ceding paragraphs, the blood of the peptonized animal shows 

 upon examination the presence of an increased amount of anti- 

 thrombin, and probably the loss or diminution in the coagula- 

 bility of the blood is due to the excess of this substance. We may 

 believe, therefore, that the peptone solution has in some way, di- 

 rectly or indirectly, stimulated the body to produce antithrombin. 

 Pick and Spiro* state that this action of peptone solutions is 

 not due to the peptone or the albumoses contained in it. When 

 obtained in purified form these substances have no such effect. 

 They attribute the action to a substance, derived probably from 

 the tissues used in the preparation of the peptone, and for which 

 they suggest the name of peptozym. 



In obtaining so-called peptone plasma by injecting solutions of Witte's 

 peptone, of the strength named, into the arteries of a dog it happens sometimes 

 that a negative result is obtained. Some specimens of Witte's peptone are 

 effective and some are not. This fact accords with the results of the investi- 

 gation made by Pick and Spiro in indicating that the reaction is not due to the 

 peptones or proteoses, but to some unknown constituent present which may be 

 regarded as an impurity. 



Leech extracts differ from solutions containing peptozym in 

 that they prevent the clotting of the blood when added to it out- 

 side the body. They evidently contain already formed a substance 

 whose action prevents coagulation. This substance is secreted by 

 the salivary glands of the leech. It has been prepared from the 

 glands in a more or less pure form, and is designated as hirudin., 

 It is a body belonging apparently to the groups of albumoses and 

 is supposed to antagonize the action of thrombin. As stated above, 

 a similar antithrombin occurs normally in circulating blood. 



Total Quantity of Blood in the Body. The total quantity of 

 blood in the body has been determined approximately for man 

 and a number of the lower animals. The method (Welcker) 

 used in such determinations consists essentially in first bleeding 

 the animal as thoroughly as possible and weighing the quantity 

 of blood thus obtained, and afterward washing out the blood- 

 * "Zeitschrift f. physiol. Chemie," 31, 235, 1900. 



