416 RESPIRATION. 



name of the " laughing gas " ; but this condition is followed 

 by anaesthesia, and finally asphyxia, probably because the 

 gas has such an affinity for the blood-corpuscles as to re- 

 main to a certain extent fixed, interfering with the inter- 

 change of gases which is essential to life. Notwithstanding 

 this, experimenters have confined rabbits and other animals 

 in an atmosphere of nitrous oxide for a number of hours. 

 In all cases they became asphyxiated, but in some instances 

 were restored on being brought again into the atmosphere. 1 



Other gases which may be introduced into the lungs 

 either produce asphyxia, negatively, from the fact that they 

 are not absorbed by the blood and are incapable of carrying 

 on respiration, like hydrogen or nitrogen, or positively, by a 

 poisonous effect on the system. The most important of the 

 gases which act as poisons are, carbonic oxide, sulphuretted 

 hydrogen, and arseniuretted hydrogen. It is somewhat un- 

 certain whether carbonic acid exerts its deleterious influence 

 as a poison, or as merely taking the place of the oxygen in 

 the blood-corpuscles. It is easily displaced from the blood 

 by oxygen, and therefore does not seem to possess the prop- 

 erties of a poison, like carbonic oxide, and some other gases, 

 which become fixed in the blood, and are not readily dis- 

 placed when fresh air is introduced into the lungs. 



Consumption of Oxygen. The determination of the 

 quantity of oxygen which is removed from the air by the 

 process of respiration is a question of great physiological in- 

 terest, and one which engaged largely the attention of La- 

 voisier and those who have followed in his line of observa- 

 tion. On this point there is an accumulated mass of 

 observations which are comparatively unimportant, from the 

 fact that they were made before the means of analysis of the 

 gases were as perfect as they now are. Though many of the 

 results obtained by the older experimenters are interesting 

 and instructive, as showing the comparative quantities of 



1 LONGET, op. tit., tome i., p. 460. 



