AIR VITIATED BY BREATHING. 



74i 



mine. Distinct symptoms are produced by air containing -05 per cent, 

 of the gas, and urgent symptoms with '2 per cent. The poisonous 

 action diminishes as the tension of oxygen increases, and vice versd. At a 

 tension of two atmospheres of oxygen this poisonous action is abolished 

 in the case of mice, and this disappearance of the poisonous action is 

 due to the fact that at high tensions of oxygen the animals can dispense 

 entirely with the oxygen-carrying function of haemoglobin, and can 

 obtain enough oxygen from the gas dissolved in the plasma of the 

 blood. 



As regards the gases of the blood, after poisoning with carbon 

 monoxide, Grehant 1 found that 100 c.c. of blood from the carotid of a 

 poisoned dog contained 6 c.c. of oxygen, 30*3 c.c. of carbon dioxide, and 

 20 c.c. of carbon monoxide ; whereas a sample of blood taken before the 

 administration of the gas yielded 19*5 c.c. of oxygen and 44'2 c.c. of 

 carbon dioxide. The following figures show the effect of different doses 

 of carbon monoxide upon the gases of the blood of dogs poisoned by the 



The administration of small doses of carbon monoxide, enough to 

 produce unconsciousness, causes a marked reduction in the respiratory 

 exchange 2 of a mouse, and its temperature falls. 



According to Gaglio, 3 carbon monoxide present in the blood is not 

 oxidised, but St. Martin 4 states that it is slowly oxidised in the 

 presence of oxyh^moglobin. The compound of this gas with haemo- 

 globin is partly dissociated in sunlight, 5 but upon these points more 

 details will be given in the discussion upon the gases of the blood. 



The respiration of air vitiated by breathing. The air vitiated 

 by respiration, as in overcrowded rooms, is distinctly unwholesome, but 

 the causes of this deleterious action are not simple, but may arise from 

 substances given off either from the lungs by respiration, from the body 

 by perspiration, or from the injurious products of disease or filth. 



Even as early as 1674, Mayow 6 had stated that an animal died if 

 kept in a limited quantity of air, because it had used up the respirable 

 portion, the nitro-aerial gas (oxygen) ; he further pointed out that re- 

 spiration and combustion produced similar changes in the air. About 

 the year 1726, Stephen Hales 7 observed by experiments upon himself 



1 Compt. rend. Soc. de biol., Paris, 1892, p. 163. 



2 Haldane, Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 430. 



3 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1887, Bd. xxii. S. 233. 



4 Compt. rend. Acad. d. sc., Paris, 1891, tome cxii. p. 1232. 



5 Haldane, loc. cit. 



" Tractatus quinque," Oxonii, 1674. 

 7 "Statical Essays," 2nd edition, vol. i. p. 2 



236 et seq. 



