382 



Drs. J. W. Pickering and J. A. Hewitt. 



Summary and Conclusion. 



1. The retardation of the coagulation of the blood resulting from the rapid 

 intravascular injection of " peptone " into either whole cats or into cats with 

 the liver out of circulation is reduced or annulled by increase of carbon 

 dioxide in the blood. 



2. The anticoagulant action of " peptone," if annulled by an increase 

 of carbon dioxide, can bo restored by administration of oxygen or of 

 excess of air. 



3. In pithed animals respiring air, the retardation of coagulation of shed 

 blood following the rapid injection of moderate amounts of " peptone," can 

 be produced when the liver is out of the circulation. 



4. Previous failures to obtain this result are due to attention not having 

 been paid to the increase of carbon dioxide in the blood of animals with 

 impaired vitality following operation and prolonged narcosis. 



5. With suitable precautions to preserve the surface conditions of the 

 blood, typical " peptone " delays of coagulation can be obtained in vitro with 

 quantities of " peptone " no greater than are required to produce a similar 

 effect in the living animal. 



6. If special precautions are not taken to preserve the surface conditions of 

 shed blood, admixture in vitro with moderate amounts of "peptone" causes 

 no appreciable anticoagulant effect. 



7. Leucocytes play no part in the anticoagulant action of " peptone " on 

 blood. 



8. It is superfluous to assume that the anticoagulant action of " peptone " on 

 blood is due to hepatic secretion of an excess of alkali under the toxic stimulus. 



9. It is unnecessary to assume that the anticoagulant action of " peptone " 

 is due to the secretion of antithrombin, either by the liver or by other cells 

 of the body. 



10. Typical immunity to the action of " peptone " on blood can be obtained 

 by injecting maximal amounts, in repeated small doses, into animals with the 

 liver out of circulation. 



11. The current hypotheses on " peptone " immunity are shortly discussed, 

 and reasons given for not accepting them. Immunity to " peptone " appears 

 to be a physical process akin to adsorption. 



12. Experiments on the perfusion of the liver do not show that anti- 

 thrombin is normally secreted by that organ. 



13. If the foregoing conclusions are correct, it follows that in the inter- 

 pretation of the coagulation of the blood it is unnecessary to assume the 

 existence of antithrombin, pro-antithrombin, and anti-prothrombin. 



