104 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
bustion ’’ is the quantity evolved when a substance, like cane 
sugar, is completely oxidised in a calorimeter, so that, in the case 
of herring flesh the heat of combustion, or energy-value, would 
be found by burning a weighed quantity of the dried substance 
and estimating the quantity of heat evolved. The latter is 
expressed in calories, a calorie being that amount of heat required 
to raise the temperature of one kilogramme of water through a 
range of 1 degree Centigrade, measured from a certain starting 
point. | 
In finding energy-values of foodstuffs it is assumed that 
the substances are as completely oxidised in the human body 
as they would be when burned in a calorimeter with all possible 
precautions of experiment. : 
In general the actual heats of combustion are not experi- 
mentally found. It is usually assumed that all“ fats” are the 
same, and that all “* proteids”’ are also the same, with respect 
each to its heat of combustion. In practice the percentages of 
‘* fat,” that is, of ether-extract, and of “ proteid,”’ that is, of 
nitrogen multiplied by the factor 6-25, are found. “ Fat” is 
multiplied by 9-3 and proteid by 4-1, and the products are added. 
together. The sum is then multiplied by 10 so giving the heat 
of combustion, or “ energy-value”’ of the foodstuff in calories 
per kilogramme. ( 
It does not follow that the heat of combustion obtained 
experimentally, is necessarily the same as the energy-value 
estimated as indicated above. Usually the difference between 
experimental and calculated energy-values is not found. In 
the case of a published series* of analyses of cooked fish the 
following values were obtained experimentally :— 
Heats of combustion Energy Values found 
found by by calculation from _ 
experiment. the analyses. — 
Flesh of Salt Herring... ... 4,134 4,352 
Flesh of Fresh Herring ... ... 4,655 5,098 
Mesh ot Spratt MOR. sa 5,326 
Meshiol Cods)1. 0 * wri/e.o indies DOK 4,138 
* Miss K. Williams, ‘“‘ The Composition of Cooked Fish,” Journ. Chem. 
Soc., Trans., Vol. LXXI, 1897, pp. 649-53. 
