«9* Report on a Memoir of M, DelarocJie, 



Monro, Av ho in his work on fishes oujrlit to have thrown 

 a great deal oF light on this suhject, has 'added but little to 

 what was known before on this subject. He made the 

 same distinction with Perrault between bladders with secre- 

 tory red bodies which have no canal, and those which have 

 a canal and want these bodies ; but he does not mention 

 any French anaioniist; perhaps because he had never read 

 any of their \' orks on the subject. 



He remarked that the genus anguilla formed an excep- 

 tion to the rule, from having the canal and red bodies. 

 With respect to the other parts of the question, he did not 

 decide upon the use of the bladder ; and merely inquired, 

 if fishes could not, in swallowing, distinguish the bubbles 

 of air from the mass of water, and make them pass in pre- 

 ference into this oroan. 



JVl. Fischer, now professor at Moscow, published in 

 1 795, atLeipsic, a particular dissertation on this subject : in 

 which after having given an cxtractof »he writing^s of his pre- 

 decessors, and having comnmnicated his own observations 

 on the carp and the tench, he hazarded the opinion, that 

 the air-bladder, independent of its uses for motion, is 

 also a supi)lementary organ of respiration, destmed to ab- 

 sorb the oxygen from the atmospheric air contamcd in wa- 

 ter, as the gills are destined, according to him, to absorb 

 The oxygen of the water itself, by decomposing it. 



M. de Lacepede supposes, that certain fishes may at 

 least fill their bladder with the gases resulting from the 

 decompositions which their respiration occasions. He 

 thought that it was frequently hydrogen with which it was 

 filled, and he mentioned tenches in which he had collccied 

 precisely this kind of gas. 



Finally, M. Duvernoy, editor of that part of Cuvier's 

 comparative anatomy which has for its object the air. 

 bladder of fishes, adopted, in common with M. Cuvier, 

 the opinion of Needham and Ka^hlrcutcr, that the air is 

 produced in the bladder by secretion. He also described 

 some of the organs of this secretion in fishes not before 

 observed ; but, from too much precipitation, he forgot to 

 advance the principal argument, founded on the absence of 

 all canal of communication in many species. He concludes, 

 from the absence of the vessel itself in fishes belonging indis- 

 priminately to all descriptions of families, aiid even to ge- 

 tiera ll'iC o^her species of which art fiunished with it, that its 

 iFunctions cannot be very essential to litf . By comparing 

 Its proportional volume with the nature of tlu* movements 

 of tyery .♦ish, and by examining the supplementary means 



grautecj 



