FOOD VALUE OF SEA MUSSELS. 
107 
the flesh of each species contained the same amount of nutrients we might conclude that 
for equal weights of the shellfish the food value of the mussel is about equal to that of 
the long clam but three times that of the oyster. This obvious superiority over the 
oyster is due to the thin, light shell of the mussel, which stands in sharp contrast to 
the heavy, thick shell of the oyster. A consideration of the chemical composition of 
these forms, however, will show that the difference in food value between the mussel 
and oyster is even greater than is indicated by the above table. 
The account which follows is taken from Doctor Alsberg’s personal report to me. In 
view of the fact that the methods used in making the analyses differ in some important 
particulars from those employed by Atwater (1891), with whose results comparisons 
are made, it is necessary to describe them briefly. 
In preparation of a sample a large quantity of the mussel meats was ground up in a 
meat chopper and the ground-up sample thoroughly mixed. Of this, a small sample 
of 50 grams was weighed out into a weighed glass dish. Enough sulphuric acid was 
added to make the reaction neutral. As the reaction of the juices of invertebrates 
is very alkaline, this is a most important matter. If it is neglected, much nitrogen is 
lost as ammonia. This precaution has apparently not been taken by Atwater or any- 
one else. Probably Atwater’s figures for oysters are too low for this reason. Doctor 
Alsberg’s high nitrogen values are probably in part due to this method. The glass dish 
containing the 50 grams of neutral material was then evaporated to dryness on the 
steam bath, with care that the reaction remained neutral. Atwater dried in a stream 
of hydrogen. There were no facilities for doing this in the present work, but it is thought 
that the results are unaffected, except to a slight extent for the fat determinations. 
The material thus dried was very difficult to pulverize, partly because of the fat 
content, which made it greasy, and partly because invertebrates contain hygroscopic 
salts. Therefore the material was boiled out with 95 per cent alcohol until the latter 
was colorless. The alcoholic solution was made up to a known volume and analyzed 
by itself. The results were added to those obtained from the residue. The sum of the 
two gives the figures for the total. The residue from the alcohol was easily ground up 
and sampled in an agate mortar. The material for all the determinations was weighed 
out at the same time. In addition, about 1.50 grams were weighed in a weighing bottle 
and dried at 6o° C. in vacuo over sulphuric acid in a Schmiedeberg drying apparatus. In 
this way the total quantity of water was determined and the determinations calculated 
accordingly. The water determinations are therefore more correct than those of Atwater. 
The fat determinations were done by extracting with carbon tetrachloride (CC 1 4 ) 
in a Soxhlet apparatus. It was not safe to use ether, as Atwater did, because of the 
danger of fire in a wooden building. As carbon tetrachloride is a better solvent than 
ether, the figures obtained are naturally a little higher than those of Atwater. Another 
reason why they are higher is that the material was not dried in hydrogen. 
Nitrogen was determined by the Kjeldahl method, which had not been discovered 
in Atwater’s time. He used the soda-lime method, which is probably as good. 
• Atwater made no determinations of carbohydrates. Inasmuch as the oyster con- 
tains much glycogen, an attempt was made to determine glycogen in the mussel. This 
