6 BULLETIN 649, U. S. DEPARTMENT OF AGRICULTURE. 
BOSTON MACKEREL. 
The investigations reported in this paper, which form a part of 
an extended study of the digestibility, nutritive value, and uses in 
the home of fish and fish products, have to do particularly with the 
digestibility of protein. One of the varieties of fish, Boston mack- 
erel, here studied in comparison with other sorts of fish, has, however, 
been considered from the standpoint of the relative digestibility of 
animal fats of different kinds in an earlier bulletin. 1 
Boston mackerel (Scomber scombrus, Linnaeus) is a highly fla- 
vored fish, which can be compared to moderately fat meat in food 
value, since it supplies good amounts of both protein and fat. This 
fish, which is found throughout the north Atlantic, spends the winter 
months in deep water; in the spring, schools rise to the surface and 
approach the land. This fish forms one of the chief products of 
the New England fisheries, the catch during the year 1916 amounting 
to approximately 16,000,000 pounds. The fish used in this inves- 
tigation were purchased at a local market and weighed, after clean- 
ing, "approximately 3 pounds each. They were procured at the 
height of the season, were in prime condition, and when prepared 
in the form of a fish loaf made a most appetizing dish. While the 
Boston mackerel possesses a characteristic flavor which is quite 
pronounced in the boiled or fried fish, this flavor was not evident in 
the fish loaf. 
Three subjects living under normal conditions, who had acquired 
considerable experience in work of this kind in connection with the 
determination of the digestibility of some of the common edible fats 
of animal and vegetable origin, assisted in this study. The results 
which were obtained in the three-day test period follow. 
i U. S. Dept. Agr. Bui. 507 (1917), p. 16. 
