698 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
ods commonly employed as to learn the amounts of the ingredients. 
The methods have proved unsatisfactory in many respects, and we have 
felt it advisable to make no more determinations by them than are 
indicated in the tables until the subject is worked up more thoroughly. 
For that matter, a satisfactory examination of the proximate constitu- 
ents will involve the study of a good deal more than the compounds of 
the flesh. Considering the complicated character of the compounds 
concerned, the vagueness of our present knowledge of them, and the 
amount of preliminary work necessary before such an investigation 
can be got into good running order; and adding to all this the impor- 
tance of studying the elementary composition of the organic compounds, 
and the mineral ingredients as well, it is clear that much labor will be 
necessary to reach the desired results. Those we have obtained will at 
least serve to compare with similar ones obtained by other analysts.* 
Cold-water extract. — Of the freshly chopped substance, 33£ grammes 
were digested for 18 to 24 (generally about 20) hours in 500 cc. of cold 
water, and then filtered. The filtration was conducted at first through 
“ coffee w filter paper, but we have found it better to use fine linen cloth, 
which has the advantages of more rapid filtration and of allowing tire 
liquid to be squeezed through with proper care. The solids do not pass 
through the cloth more than through the filter paper, and by placing on 
a glass plate, scraping, and subsequent rinsing, they are separated much 
more easily and completely than they can be from the filter paper. 
Albumen coagulated from cold-water extract. — The filtrate thus ob- 
tained was boiled and filtered through previously dried and weighed 
asbestos filters. Alter washing with ether, the filter with its contents 
was dried and weighed. That this method for determining albumen is 
accurate is by no means proven or even probable. Indeed, in some 
species of fish at least — and the same is true of other animals — the cold- 
water extract of the muscular tissues contains a form of albumen, or at 
any rate a substance or substances closely resembling albumen, which 
are not precipitated by boiling at all, except after the addition of large 
quantities of acid or salts. When the determinations in question were 
made, these substances had not been well studied, but I was persuaded 
that the method followed was not reliable for the determination of the 
actual amount of albumen, a view which studies, to be elsewhere dis- 
cussed, have amply confirmed. 
Extractive matters. Cold-water extract not coagulated by boiling. — The 
filtrate from the coagulated albumen was evaporated in platinum cap- 
sules and weighed. One portion was used for determination of the ash, 
which was done by charring at a low temperature, extracting with 
water, igniting the residue until it was well burned, adding the water 
solution, evaporating, igniting carefully at a low temperature, and 
weighing. The other portion was finely ground, dried in air to deter - 
* See Alm^n. Analyse des Fleisches einiger Fische, Nova Acta Reg. Soc. Sc. Ups., Ser. 
hi, Upsala, 1877. 
