1894.] Oxygen upon the Coagulability of the Blood in Vivo. 281 



In the three experiments last mentioned the coagulability of the 

 blood was already at a maximum when the animal was breathing 

 atmospheric air. 



It is to be noted that the blood which was drawn off while the 

 animal was breathing the carbonic acid and oxygen was arterial in 

 colour in all the experiments which have been summarised above. 

 The increase of coagulability must therefore be ascribed to the in- 

 crease of carbonic acid in the blood, and not to any defect of oxy- 

 genation. 



It has thus been demonstrated that the increase of carbonic acid 

 in the blood does exert a favourable influence on coagulation.* Car- 

 bonic acid is therefore in all probability what I assumedf it to be, i.e., 

 a vera causa in the determination of intravascular coagulation to 

 particular vascular areas. 



Effect of a Diminution of Carbonic Acid. 



This question was studied by examining the condition of coagu- 

 lability in animals when an atmosphere rich in carbonic acid was 

 replaced by (a) ordinary air, or (b) by oxygen. ' 



a. Results of experiments in which an atmosphere of carbonic acid was 

 replaced by ordinary air. The result J of such a replacement of carb- 

 onic acid and oxygen by atmospheric air is a decrease of coagulability 

 to the original norm. 



6. Results of experiments in which an atmosphere of carbonic acid 

 and oxygen is replaced by an atmosphere of unmixed oxygen. The sub- 

 stitution of unmixed oxygen for the mixture of carbonic acid and 

 oxygen is invariably followed by a decrease of coagulability. The 

 diminution may be due to a specific effect of an atmosphere of un- 

 mixed oxygen. On the other hand it may with much greater prob- 

 ability be referred to the diminution of carbonic acid in the blood, 

 for the rate of respiration is always extraordinarily accelerated (to 

 160 respirations per minute and upwards) by the inspiration of 

 oxygen. This view is also suggested by the analogy of the experi- 

 ments in which air is substituted for the carbonic acid mixture. It 

 is further supported by the fact that the diminution of coagulability 

 is apparently proportionate to the amount of carbonic acid which is 

 present in the blood. The diminution is, for instance, well marked 



* I have found this statement to hold true also in the case of human blood. The 

 inhalation of an atmosphere which is rich in CO^ causes an increased coagulability 

 my own blood. I have obtained a similar increase of coagulability (associated 

 rith an arrest of haemorrhage) in a case of severe bleeding in haemophilia. I have 

 obtained an increased coagulability by inhalation of CO 2 in the case of three 

 aembers of another haemophiliac family. 21/2/94. 



t ' Journ. of Physiol.,' vol. 12 ; ' Boy. Irish Acad. Proc.,' 3rd Series, vol. 2, No. 2. 

 This result is well shown on the protocols of rabbit 161 and dog 2. 



