RESPIRATION OF ARTIFICIAL ATMOSPHERES. 343 



symptoms of suffocation ; according to Coutenceau* and Nysten,t 

 rather more carbonic acid appears to be exhaled than in the atmo- 

 spheric air. 



The most careful experiments have been made on the respira- 

 tion of nitrous oxide by its discoverer, Humphrey Davy, and these 

 observations have been perfectly corroborated in recent times by 

 Ph. Zimmermann.:): The first effects are manifested by pleasurable 

 sensations, considerable excitement, and a state resembling intoxi- 

 cation, but this speedily (after the lapse of five or ten minutes) 

 passes into asphyxia. According to Davy's analyses of the 

 expired air, a large quantity of nitrous oxide is absorbed by the 

 blood ; carbonic acid and nitrogen being given off in no larger 

 quantities than usual. Zimmermann made numerous experiments 

 with this gas on pigeons and rabbits, and found that the pulse 

 soon became irregularly quickened, and the respiration very 

 frequent, these symptoms being followed after a time by slight 

 convulsions and asphyxia. A strong rabbit was resuscitated by 

 the artificial inhalation of atmospheric air, after the animal had 

 remained for 3 hours and 20 minutes in an atmosphere of nitrous 

 oxide. Zimmermann found that a rabbit which yielded on an 

 average 0*8 of a gramme of carbonic acid in atmospheric air, 

 exhaled 1/3 grammes, when respiring nitrous oxide. 



Respiration may be carried on without injury for a tolerably 

 protracted period in an atmosphere containing hydrogen gas, if a 

 sufficient quantity of oxygen be present. Regnault and Reiset 

 caused rabbits, a dog, and frogs to respire in an atmosphere whose 

 nitrogen had been for the most part replaced by hydrogen (from 

 55 to 77 of hydrogen, from 1*1 to 14'4 of nitrogen, and from 

 21'8 to 28'8-g- oxygen); the rabbit remained in this atmosphere 

 20 hours and the dog 10 hours without any obvious injury, 

 excepting that the respiration was augmented in force a circum- 

 stance which these observers thought they might refer to the 

 greater cooling power of the hydrogen. At the close of the experi- 

 ment nearly the original amount of hydrogen was found ; there 

 was a more considerable absorption of oxygen than in the case of 

 atmospheric air. Nitrogen appeared to be exhaled; but this 

 might have been derived from the air already in the lungs of the 

 animals, when they were introduced into the apparatus in which 

 they were made to respire. The respiration of these animals pro- 



* Revision desnouv. doctr. chem.-physiol, &c. Paris, 1814. 

 t Reclierches de Physiol. et de Chim. pathol. Paris, 1811. 

 J Diyy. inaug. med. Marburgi, 1844. 



