1902.] Influence of Oxygen on the Respiratory Exchange. 455 



there suddenly swept down the arteries gas bubbles, which drove the 

 blood corpuscles before them and filled the capillaries. 



On recompressing the frog to 70 atmospheres the gas within the 

 vessels passed again into solution and the corpuscles appeared in the 

 capillaries. 



We have made similar observations on a bat (obtained for us by the 

 kindness of Mr. F. Jones). 



We observed the circulation in the wing. The bat was hibernating. 

 The circulation was therefore slow, and the heart-beat infrequent. On 

 raising the pressure to 10 atmospheres the pulse became more frequent 

 and the capillary circulation accelerated. At 20 atmospheres of oxygen 

 the circulation continued unimpaired. On decompression after 10 

 minutes the circulation became impaired, but no gas bubbles appeared 

 in the capillaries. The animal had not, owing to the slow circulation, 

 been under pressure for a sufficient length of time to become saturated 

 with gas. 



One of us (L. Hill) has frequently noticed gas embolism to follow 

 decompression of mice and birds. The gas embolism is the cause of 

 the convulsions which follow decompression. 



Conclusion. — A rapid increase of pressure to 70 atmospheres has no 

 mechanical effect on the circulation of the blood. 



This research has been carried out with the help of a grant from the 

 Government Grant Fund of the Eoyal Society. 



" The Influence of an Atmosphere of Oxygen on the Eespiratory 

 Exchange." By Leonard Hill, M.B., F.E.S., and John J. E. 

 Macleod, M.B., Mackinnon Besearch Scholar of the Eoyal 

 Society. Eeceivecl May 22— Bead June 12, 1902. 



Eegnault and Beiset* found that the uptake of oxygen was the 

 same in 46 per cent, and in 77 per cent oxygen as in atmospheric air. 



Baul Bertf on the other hand found that the processes of oxidation 

 were most intense in 60 per cent, oxygen, while they became lessened 

 in a pure atmosphere of oxygen. Bert's figures for a rat placed for 

 24 hours in a current of air and oxygen were as follows : — 



Amount of 2 in atmosphere. 2 inspired. C0 2 expired. 



21-0 per cent 12-6 7*06 



48-3 „ 13-72 10-32 



88-2 „ 11-35 6-96 



* Eegnault and Eeiset, ' Annales de Chimie,' 20, 26 (1849). Translated in 

 Annalen der Chemie u. Pharm.,' vol. 73, p. 92. 

 t Paul Bert, " La Pression Barometrique/' p. 832 (Paris, 1872). 

 VOL. LXX. 2 I 



