FISHES IN GENERAL 237 



la ter contains will thus be obviously drawn away. But still farther, 

 how cotnes the air-bladder, according to their hypothesis, to swel 1 un 

 der the experiment of the air-pump ? What is it that closes the aper 

 ture of that organ in such a manner as at last to burst it? or what 

 necessity has the fish 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 distension of the air-bladder. Indeed, it should 

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

 sity there was for its being uselessly accumulated within ; and to n.ake 

 the modern system consistent, the fish under the air-pump, instead of j 

 permitting its bladder to be 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 quan- 

 tity 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 lesa 

 pair of muscles, for contracting or dilating this organ; its aperture is 

 from the gullet ; and what air 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 anchovy and fresh-water 

 gudgeon.* Indeed, the number of fish that want this organ is alone 

 sufficient proof that it is not so necessary for the purposes of swim- 

 ming ; and as the ventral fins, which in all fish lie flat 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 fish at different depths in the water ; 

 but whether it be to supply them with air when it is wanted from 

 without, or for what other purpose, I will not take upon me to deter- 

 mine. 



Hitherto we have seen a fish in every respect inferior to land ani- 

 mals ; 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 to mankind," 

 says Bacon, " arise from the changes and alterations of the atmo- 

 sphere ; but fishes reside in an element little subject to change ; theirs 

 is an uniform existence ; their movements are without effort, and their 

 life without labour. Their bones also, which are united by cartilages 

 admit of indefinite extension ; and the different sizes of animals o 

 the same kind, among fishes, is very various. They still keep growing 

 their bodies, instead of suffering the rigidity of age, which is the cause 

 of natural decay in land animals, still continue increasing with fresh 

 supplies; and as the body grows, the conduits of life furnish their 

 stores in greater abundance. How long a fish, that seems to have 

 scarce any bounds put to its growth, continues to live, is not ascer- 

 tained , perhaps the life of a man would not be long enough to inea 

 sure that of the smallest." 



* Redi. 



