436 BLOOD AND LYMPH. 



digestion experiments, is in reality a mixture of prot:oses and 

 peptones. When injected into the circulation in the proportion of 

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

 very greatly diminished. When, however, such solutions are added 

 to freshly drawn blood they exercise no influence upon the coagu- 

 lation. Evidently, therefore, when injected into the blood they 

 provoke a reaction of some sort the products of which prevent 

 coagulation. Delezenne's work given above offers a simple ex- 

 planation. Such solutions cause a rapid destruction of leucocytes 

 (and blood plates) with the production of leuconuclein and histon ; 

 the former substance is destroyed or removed by the liver and the 

 histon remaining in the blood is the cause of the non-coagulation. 

 Pick and Spiro * have shown 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. Leech extracts differ from 

 solutions containing peptozym in that they prevent the clotting 

 of the blood when added to it outside the body. They evidently 

 contain already formed a substance whose action prevents coagula- 

 tion. This substance is secreted by the salivary glands of the leech. 

 It has been extracted from the glands in a more or less pure form, 

 and is designated as hirudin. Nothing is definitely known regarding 

 its chemical structure or its mode of action in preventing clotting. 



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-vessels with water 

 and estimating the amount of hemoglobin in the washings. 



Grehant ("Journal de 1'Anat. et de Physiol.," 1882, 564) has devised an- 

 other method which may be used upon the living animal, as follows : A 

 specimen of blood is taken from the animal and the volume per cent, of 

 oxygen is determined by extraction with a gas-pump. The animal is then 

 made to breathe a known volume of carbon monoxid for a certain time, and 

 the total amount of this carbon monoxid that is absorbed is ascertained by 

 analysis. A second specimen of blood is then taken and its volume per cent, 

 in oxygen is again determined. The difference between this volume per cent, 

 of oxygen and that obtained before the administration of the carbon monoxid 

 gives the volume per cent, of carbon monoxid in the blood, since the latter 

 gas displaces an equal volume of oxygen. If the total amount of carbon 

 monoxid absorbed by the blood is indicated by V and the volume per cent., 

 that is, the number of c.c. to each 100 c.c. of blood, is indicated by v, then the 



total quantity of the blood will be given by the formula X 100. 

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



