206 PHYSIOLOGY. 



some time previous to operation on the gall-bladder., where there has 

 been much jaundice, to prevent the haemorrhages which may ensue 

 on account of hindrances to coagulation by the long action of the 

 bile on the blood. 



Agents are found in the blood-plasma and serum which retard 

 coagulation in the oxalate-plasma and in the sodium fluoride-plasma. 

 Also in serum, there are bodies hindering coagulation, although the 

 serum contains thrombin. Normal serum inhibits the action of 

 strong active fibrin-ferment. It must then be inferred that in cir- 

 culating normal blood there are substances which tend to inhibit 

 coagulation, antithrombins. There are bodies which act in a direct 

 manner to inhibit coagulation, like snake venom and hirudin, the 

 latter coming from the salivary glands of the leech. Hirudin has 

 chemical peculiarities like a secondary albumose, loses its powers 

 completely or in part by heating at 100 C., and dialyzes with diffi- 

 culty. This leech product acts intravascular and extravascular, and 

 is the best means in the physiological laboratory to prevent the clot- 

 ting of blood. 



This substance is supposed to be antithrombin, and thus pre- 

 vents the clotting of blood. 



In snake venoms, especially in that of the cobra, there is a body 

 which, in very small doses (0.00001 gram to each kilogram of the 

 animal), hinders coagulation in the body and in vitro. Its action 

 against the formed thrombin is less than against the formation of 

 thrombin. Peptone injections per vein and other bodies of the 

 peptone group retard coagulation. This action has been ascribed to 

 the mixture with proteoses. If the liver is excluded, peptone fails 

 in preventing coagulation ; hence the liver plays the most important 

 part in the retardation of coagulation by peptone. An antithrombin 

 exists in healthy blood to prevent clotting in the blood-vessels, and 

 is formed in the liver. The proteoses stimulate the liver to produce 

 an excess of antithrombin in the blood and the peptones in this way 

 prevent the clotting of blood. The serum of certain Italian eels 

 also prevents coagulation. 



Mellanby states that the negative phase of blood in coagulation 

 owes its fluidity to the absence of fibrinogen, cobra blood to the 

 presence of an antikinase not to an antifibrin-ferment, peptone 

 blood to the presence of an excess of alkali excreted by the liver 

 Btimulated by the injected peptone, and hirudin blood to the pres- 

 ence of an antikinase and an antiferment. 



The saturation of blood with C0 2 (thus in asphyxia the blood 



