£ .291 ] 



XLtX. Ucport made to the French Institute on a MenwiT 

 of i\[. Dklarochr 071 the Air- bladder of Fishes, Bv 



X HE mathematical and physical class instructed Messrs. 

 "Lacepctlc, Vauquelin, and myself, to render an account of 

 a mcmjir by M. Francis Delaroche on the, air-bladder of 

 lishes. 



As several naturalists have been of late employed in di- 

 recting their attention to the organ which is the object of 

 this rnenioir, and to its functions, we do not think it will 

 be improper to preface our report by a historical view of 

 what has been said on the subject ; a recapitulation for 

 which M. Dclaroche himself has furnished ua with ample 

 materials. 



The air-vessel of fishes is too remarkable, it strikes the 

 eye too forcibly on the first opening of the animal, and dif- 

 fers too much from every other organ, not to awaken the 

 attention of naturalists ; but, like most objects in compara- 

 tive anatomy, it has long produced more conjectures and 

 hypotheses than exact observations and experimental re- 

 searches. 



Rondelet * confined himself to the observation, that it 

 existed more constantly in fresh than in salt-water fishe^, 

 and that it probably serves to assist them in swimming. ,f 

 Marcus Aurelius Severinus risks an opinion that the air. 

 of this vessel was produced along with the animal; which 

 proves that he had never perceived any communicalion 

 with it outwards. 



Gauthier Needham (in 1668) was the first who entered 

 into more detailed inquiries, and inserted them in a book, 

 where no one would expect to find them ; namely, Dejor^ 

 mato fcetu f. Adopting the general idea of the utility of 

 this bladder for swimming, he explained how flat fish arc 

 enabled to do without it -, he described the two tunics of 

 this organ, as well as the varieties of its form, and the 

 origin of the canal of communication. He shows that th« 

 vessels are more abundant than are requisite for its own 

 nutrition ; that it is probable that some organic function is 

 exercised by them, and that the blood contained in them 

 has some connexion with the air: but judging that it 

 would be difficult for the air to penetrate into it from with- 

 out, in certain fishes, through substances which fill the 



• Hi St. Pise. 1554, pp. 26 and T3. 



t Bilhoth. de MarigeL ii. pp. 713 and 714. 



T 2 Stomach 



