344 RESPIRATION. 



ceeded, therefore, quite as regularly in this artificial atmosphere as 

 in ordinary air a circumstance which had already been observed 

 by Lavoisier and Seguin, as well as by Humphrey Davy. 



It is clearly shown by Regnault and Reisers experiments that 

 the only reason why respiration cannot be supported for any 

 length of time in pure hydrogen gas is, that the organism is thus 

 deprived of the oxygen necessary for life. Marchand found that 

 frogs died in from half-an-hour to an hour after being placed in 

 pure hydrogen gas ; they exhaled a much larger quantity of 

 carbonic acid in this gas than in atmospheric air, for whilst 

 1000 grammes' weight of frogs exhaled about 0'077 of a gramme 

 of carbonic acid in one hour in atmospheric air, they developed as 

 much as 0*263 of a gramme of carbonic acid in the same time in 

 pure hydrogen gas. 



Carbonic oxide gas, when mixed even in very minute quantities 

 with atmospheric air, gives rise to faintness, feelings of suffocation, 

 stupefaction and death. The fact of this being the constituent to 

 which choke-damp owes its fatal effects, has been especially 

 demonstrated in recent times by Leblanc.* 



We need hardly observe that sulphuretted hydrogen, seleniu- 

 retted hydrogen, phosphuretted hydrogen, arseniuretted hydrogen, 

 ammoniacal gas, sulphurous acid, chlorine, &c., are not merely 

 irrespirable, but are also poisonous gases, like carbonic oxide. 



Like all the other functions of the animal organism, the 

 respiration is acted upon in a definite manner by numerous influ- 

 ences of the external world. The animal body is brought into the 

 most intimate, relation with the atmosphere through the medium 

 of the lungs ; and hence the effects of various atmospheric con- 

 ditions are discernible in the different respiratory functions. In 

 consequence of these relations, we will investigate the alterations 

 apparent in the composition of the expired air during different 

 conditions of the atmosphere; amongst which the temperature first 

 claims our attention. The earliest experiments made in relation 

 to this point were for the most part limited to those animals 

 which at low temperatures either fall into a state resembling 

 hybernation, or whose vital activity is at all events more or less 

 reduced. As Spallanzani, Saissy, Treviranus, and others had ob- 

 served that insects and molluscs, as well as marmots, bats, and 

 hedgehogs, exhaled less carbonic acid in a low than in a high 

 temperature, it was at once assumed as a general proposition, that 



* Compt. rend. T. 30, p. 483. 



