282 Prof. Wright. Influence of Carbonic Acid and [Mar. 15, 



when the blood is rich in carbonic acid (e.g., in protocols of rabbits 

 Io5, 163 and 135), while there is practically no diminution of coagul- 

 ability when the blood has been adequately ventilated by respiratic 

 in ordinary air (vide second oxygen inhalation in protocol of rabbit 

 155). 



It evidently results from both these series of experiments that the 

 diminution of carbonic acid in the blood which was assumed by me 

 to afford a clue to the diminished coagulability of peptone* and of 

 blood which lias circulated through the lungs and heart alone is in 

 reality capable of exercising a well marked retarding influence upon 

 coagulation. 



Effect of a Diminution of Oxygen. 



It is extremely difficult to determine with precision what effect 

 withdrawal of oxygen exercises upon the coagulability of the blood. 

 The difficulty consists in the complication of the phenomena whie 

 are due to the withdrawal of oxygen by other phenomena which 

 due to an increase of carbonic acid in the blood. To elucidate tl 

 matter, we evidently require methods which allow of at least a partif 

 dissociation of the effects of the two gases. Such methods shoi 

 aim at (a) & limitation of the amount of carbonic acid produce 

 in the system after the oxygen is withdrawn; (6) the elimination 

 of the carbonic acid which is produced; (c) a minimising of the 

 effect of the carbonic acid increase. These objects can be partially 

 realised by the two following methods : 



1. Inhalation of an atmosphere of indifferent gas (e.g., hydrogen) 

 while provision is made for free expiration into the external air. 



This method provides to some extent for the elimination of the 

 carbonic acid which is produced after the withdrawal of the oxygen. 

 On the other hand, the method does not provide against the accumula- 

 tion of carbonic acid which must occur during the dyspnceic stand- 

 still of respiration. 



2. Substitution of an atmosphere of unmixed carbonic acid for an 

 atmosphere of carbonic acid and oxygen. 



This method presents two advantages : (a) it limits the production 

 of carbonic acid in the system, inasmuch as the withdrawal of 

 oxygen, when made under these particular circumstances, no longer 

 evokes any dyspnoeic spasms ; (6) it minimises the effect of any in- 

 creased carbonic acid tension inasmuch as such increase takes place 

 in a blood which is already almost saturated with carbonic acid. 



' ROT. Irish Acad. Proc.,' 3rd Series, vol. 2, No. 2, 1891 ; ' Roy. Soc. Proc.,' 

 February, 1803. 





