27O 
Dr Carradori, also, discovered, that these animals 
lived much longer when they were immersed in wa- 
ter that had a free communication with the atmos- 
phere, than when the air was excluded *. Accord- 
ing to Spallanzani, frogs die sooner in boiled, than in 
common water. In their respiration, they consume 
oxygen, and form carbonic acid. Those which have 
been recently fed, consume more of this gas than 
those which have suffered a long abstinence. Under 
great cold, they become lethargic, but their heart still 
continues to beat, and they still, in a smaller degree, 
continue to change the air ; but the consumption of 
oxygen increases with an increase of temperature. 
These animals also change the air by their skin, as 
well as by their lungs ; and act upon it after death, 
and under putrefaction t The ova of frogs were 
likewise found to require air to carry on their evolu- 
tion. Small tadpoles, while yet attached to the egg, 
were confined in vessels half filled with water, while 
the other half contained common air, or oxygen, or 
nitrogen gas. Those in the two former vessels were 
perfectly developed, and became large enough to 
swim about ; but those confined with nitrogen per- 
ished J. 
560. Spallanzani extended his experiments to many 
other animals of this class, and obtained similar re- 
sults. Different species of serpents he found to die 
in hydrogen gas, or when confined under water, but 
* Phil. Magaz. vol. xvi. p. 245. 
t Rapports, &c. torn. i. p. 46'S. 
t Ibid. p. 466. 
