292 Report on a Memoir of M* Delarochey 



stomach, he conjcctureil lliat this fluid is secreted there,, 

 and that it proceeds from thence into the stoniitch, where 

 U assists in tlie prr)ce!is oF digestion : he even points out 

 the red bodies which ojierate this stcrction in the snake. 



Borelli explained in detail, in 16/6, the method in which 

 the bladder is used in swimming. Me observed that fishes, 

 whose air-bladders burst, remain at the bottom of the vva- 

 ter, as well as most of those which are naturally deprived 

 of it ; and concludes that it is intended to render the body 

 of the fish sufficiently light to be in equilibrium with the 

 water: he added, that by compressing the bladder, or by 

 abandoning the air whrich it contains to its elasticity, the 

 ftsh can augment or diminish its total specific gravity, and 

 assist it in its ascent or descent. He supposed, that the 

 canal which establishes in certain fishes a communication 

 between the air-bladder and the stomach, must be a me- 

 thod of varying or renewing the quantity of air *. 



To conclude : he has neither described the varieties of the 

 structure of the bladder, nor determined in what fishes it 

 exists, and those in which it is wanting. 



Bedi resumes the observations of Needham. He added 

 some details on those fishes which have no air-bladder, and 

 on the red bodies in the interior of several of these organs. 

 He also stated, that he had m vain sought for the canal of 

 cottiiDunication in certain sea-fishes 5 but he thought that 

 it was his fault, and this opinion of the generality of the 

 existence of the canal has even reigned to the present time 

 among some others. These remarks of Redi are still to be 

 found in a book entitled, Ol>servatio7is sur les Ainmaux vi- 

 vans contenus dans les Animaitx vivans. Florence, 1684. 



Ray and Willoughby, without making fresh inquiries, 

 and without deciding on the manncF in which the air is 

 introduced into the bladder, disputed the idea of this air 

 bemg useu m digestion, and reduced the bladder to its em- 

 ployment in swimming, according to the ideas of Borelli. 

 They insisted on the muscles peculiar to certain vessels, 

 aMd mistook for them the red bodies in the interior of some 

 others f. 



The same opinion on the use of the bladder was sup- 

 ported by Preston tj by Perrault§, and by Petit ||. Per- 

 rault made the important observation, that there arc fishes 



* De Mot, j4nimaK cap. 23. De Nalatu. 



f Willoughby, thst. Pwc. 1686, pp* 12 et »eq. 



1 Phil. Trans- xix. p. 4I>9. 



C Mt'Lanii/ue des /InimmuCy pail II. ch. iii. vol ii. p. 383 of his works, l721« 



il Mem, (It Cjicadt i733» 



without 



