CONSUMPTION OF OXYGEN 117 



gases. Allen and Pepys confined animals for twenty-four hours in an 

 atmosphere of pure oxygen without any notable results ; but these 

 experiments do not show that it would be possible to respire unmixed 

 oxygen indefinitely without inconvenience. The only gas beside oxygen, 

 that has the power of maintaining respiration, even for a time, is nitro- 

 gen monoxide. This is appropriated by the blood-corpuscles with great 

 avidity; and for a time it produces excitement with delirium etc., which 

 has given it the common name of the laughing gas ; but this condition 

 is followed by anesthesia, and finally by asphyxia, probably because the 

 gas has so strong an affinity for the blood-corpuscles as to remain to a 

 certain extent fixed, interfering with the interchange of gases that is 

 essential to life. Notwithstanding this, experimenters have confined 

 rabbits and other animals in an atmosphere of nitrogen monoxide for a 

 number of hours without fatal results. In all cases they became as- 

 phyxiated, but in some instances they were restored on being brought 

 again into the ordinary atmosphere. 



Other gases that may be introduced into the lungs either produce 

 asphyxia, negatively, from the fact that they 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 that act as 

 poisons are carbon monoxide, hydrogen monosulphide and arsenious 

 hydride. Carbon monoxide unites with the red corpuscles, forming 

 carbon-monoxide-hemoglobin. This union is so stable that it paralyzes 

 the corpuscles as oxygen-carriers and produces death by asphyxia. It 

 is probable that carbon dioxide is not in itself poisonous. Regnault 

 and Reiset exposed animals (dogs and rabbits) for many hours, to an 

 atmosphere containing twenty-three per cent of carbon dioxide, artifi- 

 cially introduced, with between thirty and forty per cent of oxygen, 

 without any ill effects. 



Consumption of Oxygen. The determination of the quantity of oxy- 

 gen removed from the air in respiration is important; and on this point, 

 there is an accumulated mass of observations that are comparatively 

 unimportant from the fact that they were made before the methods of 

 analysis of gases were as accurate as now. In ' the observations of 

 Regnault and Reiset, animals were placed in a receiver filled with air, 

 a measured quantity of oxygen was introduced as fast as it was con- 

 sumed in respiration, and the carbon dioxide was constantly removed 

 and carefully estimated. In most of the experiments, the confinement 

 did not appear to interfere with the functions of the animal, which ate 

 and drank in the apparatus and was in as good condition at the end as 

 at the beginning of the observation. This method is more accurate 

 than that of simply causing an animal to breathe in a confined space, 



