[5] DIGESTIBILITY OF FISH IN GASTRIC JUICE. Hl^ 



weight of the residue left by the evaporation of the 50 cubic centime- 

 ters of the digestive mixtures, multiplied by 5, gives quite accurately 

 the amount of matter (peptones and intermediate products together 

 with some salts) dissolved from the 20 grams of flesh. Theoretically 

 there are one or two minor objections to this method, the most noticea- 

 ble, perhaps, being the variable amount of undigested residue suspended 

 in the fluid diluted to 250 cubic centimeters. The amount of space, 

 however, occupied by this matter is not large, and its influence on the 

 accuracy of the method not great. Again, by the evaporation of 

 the peptones, and drying at 110° C, there is doubtless some slight oxi- 

 dation, but still it cannot be great, as the dried residue is soon brought 

 to a constant weight. While the method seems longer than to weigh 

 the undissolved residue, it is by far more accurate, and in the end we 

 believe shorter. 



The fish experimented^ with were obtained at a local market, and, 

 while always quite fresh and in good condition, we had no means of 

 knowing how long they had been out of water. 



In all of the experiments the flesh was cooked by steaming, unless 

 otherwise expressed. 



Tables I to Y give all the data of the experiments, while Table VI 

 contains the average amounts digested of each sample of cooked flesh, 

 together with the relative digestibility as compared with cooked (steamed) 

 beef, taken as 100. 



A glance at the results of the control analyses of the gastric juice 

 alone plainly shows the constancy of its composition. The strength 

 and activity of the digestive mixture, moreover, is easily seen from the 

 amount of blood fibrin (Table IV) dissolved by 200 cubic centimeters 

 of the fluid ; an amount far in excess of the fish or beef dissolved by 

 the same quantity of fluid. 



The results of the analyses show plainly that the method adopted 

 is as good as could be expected, for it must be remembered that the two 

 results obtained from each sample of flesh are not merely from dupli- 

 cated analyses, but from duplicated digestions as well, and in these, 

 extending as they do over 22 hours, with slight variations in tempera- 

 ture and agitation, small differences are to be expected. The very great 

 divergence noticed, however, in the results obtained from diflerent 

 samples of the same species of flesh show at once that there are other 

 conditions, such as age, &c., which affect the digestibility of the flesh 

 more or less, so that, in order to obtain results from which to draw 

 strict generalizations, it would be necessary to experiment with fish of 

 diflerent species, of like age, sex, and reared under like conditions. 

 As examples of this we have the very divergent results from two sam- 

 l)les of veal, and also of two bluefish (88.69 and 73.44). As direct evi- 

 dence that age, sex, &c., do exert a modifying influence on the digesti- 



' For composition of the fish experimented with, see " ^wr Chemie dcr Fische," 

 Jkrichte der deutsch. chem. (ieselL, 1(5, 18:i!.t, by Prof. W. O. Atwater. 



