PROGRESS IN BIOLOGICAL INQUIRIES, 1939 83 
partment, Cornell University, and the United States Bureau of 
Fisheries. The principal members of the staff of the hatchery are 
C. M. McCay, Cornell University; A. V. Tunison and A. M. Phillips, 
New York Conservation Department; and C. R. Mitchell and E. O. 
Rodgers, Bureau of Fisheries. The investigations at Cortland are 
of two general classifications; the development of feeding mixtures 
and methods, and studies of the transformation of food within the 
body of the trout. 
The utilization of carbohydrates.—The inclusion of carbohydrates, 
such as sugar and starch, in fish diets provides an opportunity for 
reducing feeding costs. The greater the percentage of carbohydrate 
materials that can be used by the fish, the cheaper the diet. If 
concentrated sources of carbohydrate material are to be used to 
replace meat proteins, the fish must be able to utilize them in the 
sugar or starch form in which they are administered. A series of 
experiments designed to study the rate of digestion and absorption 
of carbohydrates was conducted. Trout are able to digest and 
absorb large amounts of sucrose (cane sugar). Coating the sugar 
with melted tallow reduces the loss in water when fed in a- meat 
mixture and the melted tallow also retards the rate of disappear- 
ance of the sucrose from the intestinal tract. The use of tallow 
introduced a fat complex into the study. The sucrose was adminis- 
tered in gelatine capsules inserted directly into the digestive tract 
by means of a fine forceps. Brook trout weighing from 6 to 14 g. 
were used in the studies. The capsule usually is penetrated in about 
1 hour and the sugar starts to dissolve in the gastric fluid. When 
the trout were killed immediately after feeding, from 96 to 100 
percent of the sugar was recovered from the digestive tract. At the 
end of 3 hours the sucrose had disappeared from the capsule entirely. 
Sucrose was administered in 10-, 25-, and 50-mg. feedings, placed 
in capsules. The experiments, in which brook trout were killed 
at various intervals of from 3 to 72 hours after feeding, showed that 
the amount of sucrose absorbed was dependent on the amount avail- 
able in the gastro-intestinal tract. No sucrose was found after 72 
hours, indicating that absorption is practically complete by that time. 
Effect of diets on the liver—Brook trout fed diets rich in cooked 
starch, sugar, or dextrin, developed Jarge livers that contained a 
high percentage of glycogen. Those fed raw starch or cellulose, 
instead of cooked starch, sugar, or dextrin, developed livers com- 
parable in size and glycogen content to the livers of brook trout 
fed meat alone. An analysis of the livers of trout fed diets con- 
taining various carbohydrates was made in terms of percentage of 
total body weight constituted by the liver, percentage of dry matter 
in the liver, percentage of dry protein in the liver, percentage of fat 
in dry liver and milligrams of glycogen per gram of fresh liver. 
Experiments on staining bones in vitreo—In experimental stream 
studies, and in some nutritional studies, it would be a great aid if 
fish could be marked by some ingredient introduced into the hatchery 
diet. Since the staining of bones in the growing fish might be de- 
veloped into a method of marking large numbers of fish, preliminary 
experiments were conducted. Madder root in the diet in a propor- 
tion of 0.5 part per hundred had produced no results at the end of 
12 weeks, when the madder content of the diet was increased to 15 
