284 Prof. Wri -lit. Influence of Carbonic Aci<1 mid [Mnr. 1?, 



2. Results of Experiments in which Oxygen was withdraum by a Substi- 

 tution of Unmixed Carbonic Acid for a Mixture of Carbonic Acid 

 and Oxygen. 



This substitution of carbonic acid for the mixture of carbonic acid 

 and oxygen tends to effectuate itself spontaneously by the slowing 

 down and ultimate standstill of respiratory movements which super- 

 vene when an animal is continuously supplied with an atmosphere 

 surcharged with carbonic acid. A defect of oxygenation was allowed 

 to supervene in this manner in five* experiments. In all these cases 

 a diminution of coagulability was observed. 



Similar experiments were performed by the actual substitution of 

 unmixed carbonic acid for an atmosphere of carbonic acid and 

 oxygen. In the fourf experiments which were performed a diminu- 

 tion of coagulability was invariably observed. 



The diminution of coagulability which is observed by either 

 variant of this method may be interpreted either (a) as an effect of 

 an excess of carbonic acid in the blood, or (6) as an effect of the 

 withdrawal of oxygen. Against the former interpretation of the 

 facts the following considerations may be urged : (1) the tension of 

 carbonic acid in the blood must already have been very high -when 

 the substitution of gases was effected ; (2) with the then obtaining 

 very slow respiratory movements the respiratory interchange in the 

 lungs must have been at a minimum. It is, therefore, unlikely that 

 any appreciable increase of carbonic acid tension can have effectuated 

 itself in the blood in the interval during which the lungs were filled 

 with unmixed carbonic acid. 



If this reasoning is valid, we must evidently interpret the diminu- 

 tion of coagulability which came under observation in all these 

 experiments as a direct result of the withdrawal of the oxygen. 



It need hardly be pointed out that this interpretation would 

 harmonise with the interpretation which has just been placed uj 

 the hydrogen experiments. 



Effect of a Restoration of Oxygen to Blood rendered Anoxyhcemic by the 

 Inspiration of Hydrogen. 



It may be premised that we have here, as in the case of the 

 hydrogen experiments, to disentangle the effects of a duplicate 

 series of phenomena, (a) the giving off of any excess of carbonic acic 

 which has accumulated in the blood, and (6) the restoration 

 oxygen to the blood. The effect of (a) would, in accordance witl 

 our previous}: experiment", be a diminution of coagulability. On tht 



* Three of these experiments will be found on the protocols of rabbit 175, dog 1 

 and rabbit 171. 



t Two of these experiments will be found on the protocols of rabbit 175 

 rabbit 171. 



J Vide mpra, Experiments on Effect of Diminution of COj. 



