Section V, 1921 [49] Trans. R.S.C. 



Studies in Anoxaemia: Oxygen Unsaturation of the Arterial Blood 

 By J. J. R. MACLEOD, F.R.S.C, and S. U. Page, M.A. 

 (From the Physiological Laboratory, University of Toronto) 



The effects produced on animals by deficiency of oxygen in the 

 inspired air are widespread, the respiratory and circulatory functions 

 being amongst the first of the body to react through changes occurring 

 in the nerve centres which control them.(l) The numerous tests of 

 the reaction of man to decreasing percentages of oxygen, which 

 formed a part of the medical examination of candidates for the 

 aviation services during the war, have furnished us with most valuable 

 information of the objective and subjective symptoms of anoxaemia, 

 but they throw very little light on the exact nature of the physiological 

 changes which are responsible for these symptoms. There have been 

 in general, two views regarding this question, the one that a lowering 

 of free oxygen in the tissue fluids itself serves to account for the 

 symptoms, and the other, that the oxygen deficiency causes secondary, 

 incompletely oxidized substances to appear and that these act as 

 poisons. (2) The following investigations have been undertaken to 

 throw light on this aspect of the problem and although they are not 

 as yet completed it has been thought advisable to place certain of the 

 results on record. 



Since the earliest effects of anoxaemia are observed most definitely 

 in the functions of the respiratory and circulatory systems, attention 

 has been paid mainly to these and since the controlling centres are 

 highly sensitive to anaesthetics the use of the latter has been avoided 

 by employing decerebrate animals for the experiments. The opera- 

 tion of decerebration was performed by the method described by 

 Sherrington only such animals as recovered entirely from the 

 shock of the operation and in which the breathing and blood pressure 

 were normal being used for the anoxaemia experiments. (3) To bring 

 about the anoxaemia the trachea was connected through a wide-bore 

 cannula with a pair of very sensitive valves, one of which (the in- 

 spiration valve) was connected with a large thin-walled rubber 

 balloon kept moderately full with a mixture of oxygen and nitrogen 

 which was delivered into it from a large (100 litre) gas meter. The 

 other (expiration) valve was connected with a Gad-Krogh registering 

 spirometer of a known capacity, the volume of respired air being 

 determined by measuring the time taken for this to fill. The arterial 



