ICHTHYOLOGY. 25 



There are other questions connected with the economy 

 of fish hardly less interesting than those already men- 

 tioned. For instance, those connected with the Food and 

 Digestive powers of Fish. It might seem that fish are 

 able to live without taking any other food than that which 

 they extract from the water which passes in at their 

 mouths. A herring has, or seems to have, no food in its 

 stomach whenever or wherever it is caught ; and nothing 

 but " a sort of yellow fluid" is ever found in the stomach 

 of a salmon ; while gold-fish will not only live for months, 

 but increase visibly in size without having positive food 

 given them. Probably fish are able to extract much 

 more nutriment from the water and from the air in the 

 water than at first might be thought possible ; and there 

 can be little doubt but that, like several cold-blooded 

 creatures, snakes and frogs to wit, they can endure long 

 periods of fasting. Still, as a matter of fact, they do eat ; 

 and that most voraciously at times, as any one may see 

 by opening the miscellaneous larder of a jack, or an 

 aldermanic trout when gorged with the tender may-fly ; 

 and though gold-fish will live very long without food, they 

 most greedily devour crumbs of bread, and worms when 

 given to them. That the digestion of fish is very quick 

 is shown by the fact that solid food is reduced to a pulp 

 very soon after being taken ; and certain it is that the 

 gastric juice is most powerful in many fish, particularly 

 so in the jack, who can digest a gorge-hook with its lead 

 within a few days ; and it has been proved by experiment 

 that eels, carp, bream, and other fish can digest food 

 given to them in metal tubes. This is very strange; 

 inasmuch as the general law seems to be that rapidity of 

 digestion depends in a great measure upon the degree of 



