SEA-FISHERIES LABORATORY. 105 
These results apply, of course, to the dried flesh. The 
differences are notable, and whether or not they are of signifi- 
cance depends upon the use to be made of the results. 
Thus the “ energy-value ” of fish-food stuff must not be 
taken at its “face value.’ Very little is known as to the 
chemical] nature of the proteids and fats (or rather oils) in the com- 
mon species of British fishes used as food, for in most cases the 
proteid-values are (experimentally) nitrogen-values, while the 
‘* fats ” are always ether-extracts and are thus mixtures, which 
are probably rather different in different species and even in 
the same species of fish caught on the same fishing ground but 
at different seasons of the year. Further the energy-values 
ought (as we shall see later) to be deduced from analyses which 
_ giye the composition of the fish at all seasons, and not at some 
particular time. It is, of course, well known that the “ con- 
dition’ (that is the nutritive value) of all species of fishes 
varies largely throughout the year. Thus the flesh of mature 
plaice and cod is more “ watery”’ at the time shortly after 
spawning occurs than at any other seasonal phase. Plaice which 
have immature sexual organs are in very poor “ condition ”’ 
during February and March, the months of minimal sea-tem- 
perature. Thus two factors affect “‘ condition,’ and so energy- 
value—the sexual phase and the sea temperature. Analyses 
must be made at all stages and periods if they are to be made 
use of to furnish energy-food tables. So far as I can find, such 
series of analyses have only been made for the Herring.* 
The effects of cooking and methods of preservation and 
curing must also be considered. 
Effects of Cooking and Curing Methods. 
So very little is known with regard to the effect of cooking 
and of methods of salting, drying, smoking, &c., that energy- 
values become still more doubtful when used in dietetic dis- 
* By Milroy, loc. cit., and by myself. 
