252 
they died in two days, in a bottle quite filled with 
water, and closely stopped ; and the water, when ex- 
amined, contained no oxygen gas *. 
538. We have before detailed (55.) the accurate 
experiments of M. Vauquelin, on slugs and snails, 
which belong to the third or Mollusca class. He 
found that the oxygen gas of atmospheric air was 
completely changed into carbonic acid, without any 
alteration taking place in the whole bulk of air em- 
ployed, or in the quality of its nitrogenous portion. 
Consequently, the bulk of acid gas produced must 
have exactly equalled that of oxygen gas lost, and no 
portion of oxygen could, therefore, have been retain- 
ed in the animal system. 
539. We have already endeavoured (56. et seq.) 
to point out the fallacies in Spallanzani's experi- 
ments, which seemed to militate against these con- 
elusions. Of this writer's labours, three additional 
volumes, containing reports of several thousand ex- 
periments, have been since published by M. Sene- 
bier f. They do great credit to his industry, but, 
for accuracy and precision, they will not bear a com- 
parison with those of the justly celebrated chemist, 
whom we before mentioned. In these experiments, 
the changes produced in the air by living animals, by 
animals recently dead, and by others under a state of 
putrefaction, form the chief subjects of investigation. 
In all cases, the oxygen gas of the surrounding air 
* Treat, on Air ar>d Fire, p. 167. 
t Rapports de 1'air avec les etrcs organises, tomes iii. a Ge- 
neve, 1807. 
