104 
BULLETIN OF THE BUREAU OF FISHERIES. 
proportion of the undigested (fecal) nitrogen is due to the cracker-dust protein, which is known to be 
less digestible than ordinary flesh proteins. Consequently, in order to determine the digestibility of 
the meat proteins alone, a correction must be applied for the undigested vegetable protein. Unfor- 
tunately, we lacked time to determine this correction. 
The urine curves must be considered in pairs, because the amount of nitrogen given in the raw-beef 
and steamed-squid diets was greater than that given later in the steamed-beef and mussels ration. 
The beef and squid (upper) curves show that the beef protein was metabolized more rapidly, as the beef 
curve rises more rapidly after feeding. The difference is not great, however, and the total amount 
of squid nitrogen metabolized and excreted in the urine in twenty-four hours is slightly the greater, 
coinciding with the fact that less squid nitrogen was found in the feces. Apparently squid proteins 
are digested slightly less rapidly than those of beef, but more completely 
The steamed-beef and Mytilus curves show a similar relation, the beef being metabolized more rap- 
Fig. i. — C urves showing results of metabolism experiments. Figures on base line indicate number of hours 
since feeding. Figures in vertical line at right show number of grams of nitrogen excreted in urine. 
idly in the hours immediately following feeding, the Mytilus curve overtaking and passing the beef 
curve later, however. 
The raw-beef figures are taken from three successive days’ results, the figures for the other meats 
from the results of two days’ experiments each. The brief time (less than three weeks) available pre- 
cluded longer tests, which would have been desirable, and limited the experiments to those above 
reported. They must be regarded as merely preliminaries to a thorough investigation of the problem. 
It is clear, from the evidence just presented, that the mussel measures up well to 
the standard of digestibility. It agrees well with the consumer and the rate of digestion 
and proportion of nutrients supplied to the body approximate very nearly those of 
steamed beef. 
