318 DISTVRBAyCES OF CIRCULATION 



planation is that the leucocytes do not liberate their coagulating sub- 

 stances until they have been injured by contact with some foreign 

 body, and the experiment proves the importance of this action of the 

 leucocytes, as well as explaining wliy the blood does not coagulate dur- 

 ing life. The classical experiment of the ligation of a vein without 

 injury' to the endothelium, which permits the blood to remain stag- 

 nant for a long period without clotting, depends upon the same fact, 

 namely, that normal endothelium neither liberates coagulin itself nor 

 injures the leucocytes so that they disintegrate. Loeb recalls the 

 observation of Overton that lipoids are important constituents of the 

 cell membranes, and suggests a similarity between the vessel lining 

 and the oiled cannula, but analyses of aortic endothelium have shown 

 a rather low lipin content (8.41-9.25 per cent.), although peritoneal 

 endothelium has much more (13 to 15 per cent.).^^ The suggestion 

 that the vessel walls contain an anti-coagulin could not be confirmed by 

 Loeb. Since leucocytes are constantly undergoing disintegration in 

 the blood and tissues under normal conditions, it might be asked why 

 they do not cause clotting then and there. In explanation Loeb ad- 

 vances his observation that the coagulins are destroyed during cell 

 autolysis, and suggests that when leucocytes normally disintegrate, the 

 coagulins are first destroyed by autolysis. It has also been shown that 

 the cells and serum contain substances which inhibit or prevent coagu- 

 lation, and it is possible that these play an important part under nor- 

 mal conditions in preventing coagulation by products of cell disintegra- 

 tion, much as other antienzymes are supposed to act in preventing 

 autodigestion of living cells. 



Coagulation of drawn blood may be retarded experimentally by re- 

 moval of the calcium by precipitation as oxalate, fluoride, etc. ; also by 

 diminishing the oxygen and increasing the COo, by addition of solu- 

 tions of neutral salts in large amounts, l)y diluting greatly with water, 

 or by keeping the blood cold. Coagulation may be hastened by moder- 

 ate heat, by whipping, exposure to air, by contact with much foreign 

 matter, and by the addition of watery extracts from many different 

 tissues and organs. Poisons that destroy the ])latplets reduce the 

 coagulation (Duke). Of particular interest i)ath<)l()gically is the re- 

 tardation of coagulation that follows injections of proteoses (the so- 

 called "peptone" solutions) and also various other protein-containing 

 solutions, such as organ extracts, bacterial toxins, snake venoms, eel 

 serum, extract of leeches or of Vneinarm, impure nucleo-protein solu- 

 tions, or solutions of various colloids. ^lost of tlies(^ substances (>. g., 

 peptone, eel serum) cause reduction of coagulability when injected 

 into animals, and are without effect on blood removed from the body. 

 A few, however, prevent coagulation of di-awn blood (snake venom, 

 extract of leeches). When substances of the first class are injected 

 in sufficient f(uantities, there occurs first a period of accelerated co- 

 st Tait. Quart. .Iniir. Exj.. Physiol., ini.T (8), 301. 



