46 American Fisheries Society 



It is possible that the lesser effect of the latter in producing growth 

 was due to the fact that in the process of boiling, some of its 

 "water soluble" growth-stimulating stuffs have been dissolved 

 out. The fact that the food which has been boiled and thus lost a 

 large part of its water content was as well utilized by the trout as 

 raw meat, suggests that it would be practicable to utilize thor- 

 oughly desiccated food as trout diet. This soaked in water before 

 feeding would probably retain both its gustatory quality, as well 

 as its growth-promoting quality. This could doubtless become an 

 excellent method for preparing on a large scale and distributing 

 the food for trout hatcheries. Experiments which were planned 

 with a view of studying the metabolic value of such desiccated 

 foods, remained unperformed owing to the unexpected interruption 

 of the investigation. 



FEEDING BEEF LIVER. 



Beef or pig liver is one of the staple diets in trout hatcheries, 

 and a series of experiments were started to study its nutritive 

 value. The liver was freed from all blood vessels and ducts, and 

 the parenchyma alone was frozen solid and ground in a meat 

 grinder to a fine pulp. The food was then kept in the refrigerator 

 and analyzed as usual. Unfortunately it was impossible to feed 

 this food directly from forceps as was done with the beef heart. 

 It was necessary instead to throw a quantity of food into the 

 aquaria and leave it there for a half hour. The trout was then 

 removed to another aquarium with fresh water, in which the 

 excreta were collected, while the unconsumed food was collected 

 over glass wool in a large filtering tumbler. The filtrate was made 

 up to a definite volume, of which aliquot portions were used to 

 determine the nitrogen, fat and sugar that was dissolved out from 

 the food by the water. The solid residue was dried at 100°, 

 powdered and the composite sample for the entire experimental 

 period was analyzed in the usual way. 



Knowing the quantity of food thrown into the aquarium, the 

 amounts of nitrogen, fat and carbohydrate were computed from 

 the analytical data pertaining to the particular food sample. 

 From this was subtracted the amounts of nitrogen, fat and carbo- 

 hydrate both dissolved in the water and found in the solid residue. 



