1..j2 histokv of 



ot liie air-pump ? V.'hat is it that closes the apti tuie ol' that 

 organ in such a manner as at last to burst it? or what necessity 

 has the lish for dilating it to that violent degree? At most, it 

 only wants to rise to the surface ; and that the fish can easily do 

 without so great a distention of the air-bladder. Indeed it should 

 rather seem that the more the air was wanted without, the less 

 necessity there was for its being uselessly accumulated within ; 

 and, to make the modern system consistent, the fish under .the 

 air-pump, instead of permitting its bladder to burst, would 

 readily give up its contents ; which, upon their supposition, all 

 can do at pleasure. 



But the truth is, the fish can neither increase nor diminish the 

 quantity of air in its air-bladder at will, no more than we can 

 that which is contained in our stomachs. The animal has no 

 one muscle, much less a pair of muscles, for contracting or di- 

 lating this organ ; its aperture is from the gullet ; and what aii 

 is put into it must remain there till the necessities, and not the 

 will of the animal call it forth as a supply. 



But, to put the matter past a doubt, many fish are furnished 

 with an air-bladder, that continually crawl at the bottom ; such 

 as the eel and the flounder ; and many more are entirely without 

 any bladder, that swim at ease in every depth ; such as the an- 

 chovy and fresh-water gudgeon. ' Indeed, the number of fish 

 that want this organ is alone a sufficient proof that it is not so 

 necessary for the purposes of swimming ; and as the ventral fins, 

 which in all fish lie fiat upon the water, seem fully sufficient to 

 keep them at all depths, I see no great occasion for this internal 

 philosophical apparatus for raising and depressing them. Upon 

 the whole, the air-bladder seems adapted for different purposes 

 than that of keeping the fis^h at different depths in the water ; 

 but whether it be to supply them with water when it is wanted 

 from without, oi for what other purpose, I will not take upon me 

 to determine. 



Hitherto we have seen fish in every respect inferior to land 

 animals ; in the simplicity of their conformation, in their senses, 

 and their enjoyments ; but of that humble existence which they 

 have been granted by nature, they have a longer term than any 

 other class of animated nature. " Most of the disorders incident 



1 Redi. 



