Morgulis. — Studies on Fish Nutrition 39 



and kilogram. This very high nitrogen elimination was followed 

 by a decided drop in the next week, when it was only 71 mg. ; the 

 loss in weight at the same time having been reduced to 1.3 per 

 cent. During the entire two-weekly period of fasting 5.9 per cent 

 of the body weight was lost, and the daily nitrogen elimination 

 per kilogram of fish was 105.5 mg. The very high nitrogen elim- 

 ination during the first few days of fasting which, in this case, 

 was preceded by abundant and unrestricted feeding, will be 

 observed in several other experiments. This condition is met 

 with also in the case of the higher vertebrates. 



In experiment F-3 it will likewise be observed that the nitrogen 

 elimination reached a very high level of 132.2 mg. per day and 

 kilogram, but the fast was not continued further with this animal. 



Experiment F-4 presents essentially the same picture. This 

 trout was used in a long feeding experiment, and for weeks it was 

 fed regularly and ad libitum. It was then subjected to a fast of 

 two weeks' duration, during which time it had lost 9.3 per cent of 

 its weight. The nitrogen eliminated in the first and second week 

 shows that it was twice as large during the former, being 155.9 

 mg. nitrogen per day and kilogram for the first seven days, and 

 only 79.3 mg. for the next seven days. This large loss of nitrogen 

 observed invariably upon changing from an abundant diet to 

 fasting, especially in the case of trout F-4 which for a month 

 previous to the fast has been eliminating a fairly constant amount 

 of nitrogen daily, brings up again the question of the circulating 

 protein which, when the income of new food material is stopped, 

 is the first to be consumed. 



Experiment F-5 like the first of the series, is interesting because 

 this trout was not on an abundant diet previous to the fast. Its 

 nitrogen elimination for eight days was 91.6 mg. per day and 

 kilogram of body weight. We may regard, therefore, the elimina- 

 tion of 80 to 90 mg. per day and kilogram as the normal nitrogen 

 catabolism of the Brook Trout. (See Table I.) 



FEEDING RAW BEEF HEART. 



Raw beef heart cut in fine strips about one cm. long was fed 

 directly from forceps. The results of an experiment which lasted 

 over two months are recorded in Table II. During this time the 

 excreta for every forty-eight hours were collected and analyzed 



