on the Air-hh^ldps of Fishes^: \\ $95 



granted to those who have it not> and the various eflfeots of 

 th6se means, lie arrives at the conclusion that it is essen- 

 tially an organ connected with loco-motion. 



lie expresses his astonishment at the discordance hetwecn 

 the analysis hitherto given of the air contained in this blad- 

 der; some, like M. Fourcroy, having found hardly any thing 

 but azote; others, like M. Configliati, havjng found so 

 much as 40*0 of oxygen ; while others, like Mr. Broadbcli, 

 found the quantity variable in the same kind of fish ac- 

 cording to circumstances. M. Duvernoy concludes with 

 suggestnig that chemists should inquire into the causes and 

 limits of these variations ; a precise knowledge of which 

 could alone decide a great number of the questions in 

 dispute. 



Messrs. GeoflT.oy and Vauquelin on one hand,,, and 

 M. Biot on the other, have recently made a great part of 

 the experiments which were pointed out as requisite by 

 M. Duvernoy. 



M. Biot, in his first voyage to Tvica, examined the air in 

 the bladder of several fishes of the Mediterranean, and found 

 that it varied from pure azote up to S70 of oxygen, with 

 very little carbonic acid, and without any hydrogen, and 

 that in general the oxvgen is the more abundant, in com- 

 parison to the azote, as the lish comes from a greater depth, 

 althougl) the water at these great depths does not contain a 

 purer air than that which is at the surface. 



■ He also made the curious observation, that in fishes sud- 

 denly drawn from a great depth, the air-bladder ceasing to 

 be cx)mpressed by the enormous column of water which 

 bore upon it, is dilated so suddenly that it tears the intes- 

 tines, and is ejected from the mouth. As to the origin of 

 the air contained in it, he seems tu think it has been se- 

 creted. 



The experiments of Messrs. Vauquelin and GeofTroy, pub- 

 lished by M. Biot, confirm his own on the subject, so far 

 as the fishes on which they were made, living in our fresh 

 waters and at very small depths, gave but very little oxygen. 

 Thev agree also with other more ancient experiments of 

 M. F(mrcrov, who had found nothinir in the bladder of the 

 carp but az<;te ahnost pure, and with the analysis made 

 by M. Humboldt of the air in the bladder of the gymnotus 

 electricus, which consisted of 96-0 of azote and 40*0 of 

 oxygen. 



Such WHS the whole of our knowledge of the air-bladder 

 of fishes when M. Delaroclie read his memoir to the Instir 

 tute. But in order to complete ,the. series of facts which are 



T 4 necessary 



