71 



,59. But not only does Spallanzani dissent from 

 the conclusion of Vauquelin, as to the complete de- 

 struction of oxygen gas by the respiration of snails : 

 he contends likewise, that a portion of the nitro- 

 gen gas at the same time disappears. He placed dif- 

 ferent single snails in several equal bulks of atmo- 

 spheric air, where they remained till they ceased to 

 exhibit any signs of life. To ascertain the con- 

 sumption of nitrogen gas, he passed the residual air 

 into the eudiometrical tube through mercury, and 

 compared its bulk with that which it possessed be- 

 fore the snails were placed in it. Having then as- 

 certained the complete destruction of the oxygen 

 gas, by the test of phosphorus, he next withdrew the 

 carbonic acid by means of lime-water ; and every 

 degree of diminution beyond ~, which he considers 

 us the proportion of oxygen gas contained in atmo- 

 spheric air, was referred to the destruction of the ni- 

 trogenous portion of the air *. 



60, But, in these experiments, he has overlooked 

 many circumstances which ought to have been at- 

 tended to : and hence the results differ so much as 

 to render the conclusion quite unsatisfactory. In 

 two instances, - of the oxygen gas of the air disap- 

 peared, and from five to ~ of the nitrogen : but, 

 in two others, only ^ or ^ of the former were 

 lost, and from three to ~ of the latter ! Where, 

 in one experiment, two snails were confined together, 

 the air lost ~ of its oxygen, but only ~ of its ni- 



Memoirs on R"Pp!ratipn, p. 162, f Void. p. 



