38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 60 



general rule that the animals died when the CO, increased to 12 to 

 13 per cent and the oxygen diminished to 5 to 6 per cent. 



The death of animals confined in a small chamber is due to 

 deficiency of oxygen, which has its effect before the C0 2 rises to a 

 poisonous level. " The duration of life in such conditions is very 

 perceptibly shortened through the influence of a higher as well as a 

 lower temperature than 18 to 20 C." If the oxygen be kept above 

 6 per cent, animals may live for hours even when the C0 2 rises to 

 20 per cent or more. " An atmosphere consisting of 90 per cent oxy- 

 gen and 10 per cent nitrogen does not support life quite as long as 

 does ordinary atmospheric air when the temperature is o° C, while 

 at a temperature of 50 C. the atmosphere rich in oxygen supports 

 life much longer than the ordinary atmosphere." 



We can scarcely explain these interesting results on the ground that 

 the high concentration of oxygen lessened the respiration, metabolism, 

 and formation of body heat — an effect advantageous in the high tem- 

 perature but not in the low. It is more likely that oxygen maintained 

 the beat of the heart by lessening the production of lactic acid, and 

 thus had the same sustaining effect as we have found in men carrying 

 out strenuous work. The experiments are few, need further con- 

 firmation, and suggest enquiry. 



In the case of other animals enclosed in a chamber, the air con- 

 fined was driven to and fro in the chamber through potash tubes, 

 so that the C0 2 was absorbed. No deleterious effect developed from 

 the continual rebreathing of this air. We must conclude from all 

 these experiments that so long as the oxygen is sufficient and the CO, 

 does not rise to a poisonous level, and the temperature is kept normal, 

 the animals do not suffer, and there is no evidence of the presence 

 of any exhaled organic poison. 



Thirty-three experiments of the Brown-Sequard type were per- 

 formed by the authors. The animals were confined one in each of a 

 series of bell glasses, through which air was aspirated. 



To begin with, trouble was experienced owing to the difficulty 

 of making the connections air-tight. Failure to do so led to failure 

 of ventilation and to death from asphyxia, with the ordinary post- 

 mortem appearances. None of the focal necroses or peculiar degen- 

 erative changes recorded by Brown-Sequard and D'Arsonval were 

 noticed. " From the data accumulated with reference to the composi- 

 tion of the atmosphere in these bell jars by repeated analyses at 

 short intervals, compared with the results reported by Brown- 



