120 RESPIRATION. L.ECT. VI. 



nute. According to Lavoisier and Seguin, the oxygen con- 

 sumed in the respiration by an adult man, weighs 1015 

 grammes [about 15,675 troy grains.] The quantity which 

 disappears during respiration in man and birds is, by volume, 

 nearly equal to that of the carbonic acid evolved. Some 

 very accurate observers have found that the volume of oxy- 

 gen absorbed is greater than that of the carbonic acid pro- 

 duced. This difference is especially manifest in the carni- 

 vora, in which Dulong found that the oxygen which disap- 

 pears is sometimes double the volume of the carbonic acid 

 formed. 



By making an animal respire in a definite volume of air, 

 Dulong and Despretz have proved beyond question, that a 

 remarkable quantity of azote is always produced. This 

 fact shows that the excess of azote thus exhaled comes from 

 the aliments, and perhaps also from that azote which, as 

 we stated, is found in the stomach and intestines as the re- 

 sidue of the air introduced with the food. And if the quan- 

 tity of azote contained in atmospheric air be invariable, 

 Boussingault has demonstrated that this arises from the fact 

 that some plants absorb this gas. 



The same changes which respiration produces in the com- 

 position of atmospheric air, also take place in the air dis- 

 solved in water. We know, that in both common and sea 

 water there exists, dissolved, a certain quantity of atmo- 

 spheric air, which may be disengaged by ebullition, by- 

 bringing it in contact with some other gases, or by putting 

 the water in vacuo. These phenomena, which are alto- 

 gether physical, take place, according to the well known 

 laws of the absorption of gases by liquids, discovered by 

 Dalton. 



The experiments of Morren, likewise prove that a certain 

 quantity of carbonic acid is dissolved in these waters, and 

 \vhich seems to vary in the inverse ratio of the oxygen 



