on the A'lr-hladder of Fishes, 293 



wiihout any canal, and that it is in the latter that the red 

 bodies are found, which arc intended for the separation of 

 the air. He added, that in those which have a canal, the 

 air does not issue from the bladder, although it be com- - 

 pressed; a remark too much generalized. 



Petit, on the contrary, thought he had discovered in the 

 canal of the carp, valvuli which admit of the air escaping, 

 but not pf returning. 



Notwithstanding the observation of Perrault, Artedi still 

 ascribed to all bladders a qanal destined, according to him, 

 for the introduction of air: but, with the exception of Bo- 

 relli's*, there is no opinion given respectmg their use. 



It is the same case with Gouan, Bloch, and a variety of 

 other authors, who add nothing in other respects to the 

 details previously acquired. 



But, admitting in its fullest extent this chief employment 

 of the air-bladder, we might still suppose it to have acces- 

 sory uses, and in particular we must defer giving any opi- 

 nion as to the origin of the air which it contains. 



This was the conduct pursued by Vicq d'Azyr in 1773 J. 

 He imagined that the air originated in the stomach, from 

 whence it entered, charged with nutritive particles, into the 

 air-bladder, in order to be absorbed by the vascular system. 

 He was followed by Broussonnet in this idea§ under some 

 modifications. 



Erxleben entertained the same idea respecting the propa- 

 <rationof the air ; but as to its uses he followed the common 

 opmionll- 



These three anatomists seem to have been ignorant that 

 the communication between the stomach and the air-blad- 

 der is frequently wanting. 



This is stronglv insisted,upon by Koshlreuter^ in an ana- 

 tomical description of the lotus. After having ascertained 

 the defect in the canal, and that a number of other fishes 

 are also without it, and after having described the organi- 

 zation of the red bodies, he maintained that the air is sepa- 

 rated from the blood in the bladder. He thought his sy- 

 stem was new, not having read the writings of Perrault and 

 Needham. 



Leske adopted the opinion of Kcehlreuter **. 



.f 



* Partes Piftr. ITf^, p. 36. f Hist, des Po',wo77.t, 1770, p. 81. ' 



f Mt'mnires pre<;er>trs^ tome vii.; and hi*3 Pljysiological W^orks, tome ii. p,203, 

 § Fz/r. Posf.t. rur. liespir. sect. V. ....,., , i \ 



\\ 1776, in a memoir on the subject; and also in his Natural History, edit. 

 1797. p. 279. ''- ' • '^ 



1 Ncv. Conim. Petropqlit. tome xlx. 1775. ** Hist. Xat. 1T24, p.. 390..* 



T 3 Monro, 



