Morgulis. — Studies on Fish Nutrition 45 



raw meat. The per cent of nitrogen and fat in the dry feces is 

 much greater than on a diet of raw meat, and this condition is very 

 general as can be seen by comparing the data in columns 5 and 6 

 of Table VI. This very high percentage, however, is of no sig- 

 nificance, being merely due to the fact that the feces is more 

 compact and dry when the trout are kept on the cooked meat 

 regime. It is more significant that the amount of dry feces pre- 

 sents the same proportion of the dry matter of the consumed food 

 (3 to 4 per cent) no matter whether the food has been cooked 

 or not. 



The results of experiment 00.3 are essentially the same, though 

 this trout has shown a somewhat smaller increase in weight. 

 Experiment 00.4 which lasted forty-eight days, was made on a 

 trout which had been fasting a week before the experiment com- 

 menced. The protein of the food was utilized as usual — 95.7 per 

 cent — but only 92.5 per cent of the fat was utilized. This is 

 further confirmation of the point emphasized already on several 

 occasions in this paper of the defective utilization of fat by trout 

 that have undergone even a brief starvation. The amount of food 

 this trout ingested per day and kilogram of body weight was 10.11 

 grams. The daily increment in weight per kilogram was 4.25 

 grams; in other words, the growth index was 42. When we com- 

 pare the relative value of cooked and raw meat as the diet for 

 trout, we can indicate the following advantages of the latter: Its 

 greater palatability and greater growth-promoting quality. This 

 can be seen at once when the average "growth index" of the 

 experimental series 000.5 to 000.7 which is 45, is compared with 

 the same of the experimental series 00.2 to 00.4 which is only 39. 

 This might perhaps be objected to on the ground that the difference 

 in the body weight increments is due rather to the great difference 

 in the quantity of food which the trout have consumed in these 

 two series of experiments. It must be recalled, however, that the 

 "growth index" does not furnish information as to the actual or 

 absolute increment in body weight, but indicates the fraction 

 of the nutrient material which has become permanently incor- 

 porated as a part of the organism. The two kinds of food have 

 been apparently ample in amount to insure not only maintenance, 

 but a further increase in weight, but in the case of the cooked 

 beef heart a smaller relative increase in body weight was secured. 



