94 STORRS AGRICULTURAL EXPERIMENT STATION. 

HEATS OF COMBUSTION OF CARBOHYDRATES OF DIFFERENT 
FOOD MATERIALS. 
The ordinary meats and fish used for food contain very little 
of carbohydrates. Muscular tissue has a small quantity of 
glycogen, but in ordinary analyses it is usually not taken into 
account. As has already been stated, the protein as computed 
by the usual factor for animal foods (6.25) is probably slightly 
too large. On the other hand, the fuel value* of muscular 
tissue is not far different from that of glycogen. Hence the 
error involved in neglecting the glycogen in meats and fish as 
is ordinarily done is of little practical importance. ‘The pro- 
portion of glycogen in the livers of animals used for food, and 
in oysters and other shell fish, is considerable. ‘The amount 
of these food materials consumed in the ordinary diet is, how- 
ever, relatively small. The heat of combustion of the glycogen 
can be taken at 4.2 calories per gram. 
Milk contains a relatively large amount of milk sugar. The 
figures for heat of combustion of milk sugar now on record are 
not in agreement. We may take the factor 3.9 as most nearly 
representing the heat of combustion per gram of the carbo- 
hydrates of dairy products, and since in the ordinary diet the 
quantity of glycogen is relatively very small, this same factor 
(3.9) may be considered as an approximate average of the 
heats of combustion of all carbohydrates occurring in animal 
food materials. 
The carbohydrates of the vegetable food materials consist 
largely of starch, sugar and fiber (cellulose), with smaller 
amounts of pentosans, dextrins, gums, etc. In flours and 
meals the carbohydrates consist almost entirely of starch. 
From the data available it seems probable that on the whole 
we shall not err greatly in assuming: that 97 per cent. of the 
carbohydrates of cereal products is starch (and fiber), 2 per 
cent. dextrin, and 1 per cent. sugar. While the fiber is not 
as digestible as the starch, and would therefore not have as 
high fuel value, it occurs in such small quantities as to be of 
little importance in the cereal products as ordinarily used for 
the food of man. 
The heat of combustion of starch (and fiber or cellulose) is 
about 4.2, that of dextrin 4.1, and that of cane sugar 3.96 

* See p. 96, ef seq. 

