[3] DIGESTIBILITY OF FISH IN GASTRIC JUICE. HH 



obtained, thoroughly sampled, and then placed in a tightly stop- 

 pered bottle and kept in a cool, dry place to prevent change. The 

 acid used was pure hydrochloric of exactly 0.2 per cent strength. 

 From this material fresh gastric Juice was made for each series of ex- 

 periments, 5 grams of the pepsin being dissolved in 1 liter of the dilute 

 acid. This furnished a digestive mixture of suitable strength, and, as 

 subsequent experiments showed, well adapted to the purpose. 



Preparation of the flesh. — In order that a fair sample of the flesh 

 might be obtained in each case, 100 grams, freed from tendons, fat, 

 skin, and bones, were weighed off and finely divided by choi^ping. 

 Small portions of the sample tissue were then taken for a determi- 

 nation of the amount of solid matter,^ and then two portions of 20 grams 

 each were weighed out to determine the digestibility. These two latter 

 portions were placed in small porcelain mortars covered with watch 

 glasses, and then set into a steam-bath heated by a large gas flame for 

 30 minutes. This bath was a small copper oven, on the bottom of 

 which was a layer of water 1 or 2 inches in depth, while some distance 

 above this was placed a perforated plate upon wl)ich the dishes were 

 set, the whole provided with a tightly fitting cover, with a small outlet 

 for the escaping steam. Heated in this for half an hour the fish or 

 meat was thoroughly and evenly cooked without loss of any extractives, 

 and being in mortars, the tissue after steaming could be ground up 

 fine without loss. The flesh was then ready for digestion. 



The digestion. — As already stated, two separate or duplicate deter- 

 minations were made of each sample. Each i^ortiou of 20 grams was 

 placed in a beaker with 200 cubic centimeters of the standard gastric 

 juice, covered with a watch glass and set into a bath heated at 38^* to 40° 

 C. for 22 hours with occasional stirring. This bath consisted of a metal 

 box with a movable cover, and having about midway of its height a 

 perforated plate upon which the beakers were placed. The bath was 

 filled with water to such an extent that the beakers were immersed 

 about half an inch. The space above, when the bath was closed, was 

 of course saturated with aqueous vapor, and thus any evaporation of 

 the contents of the beakers was prevented. The temperature was kept 

 quite constant by a small gas flame, and the extreme variations were 

 not more than 35° to 42^ C., these occurring only during the night and 

 early morning. The length of time the mixtures were heated, namely, 

 22 hours, was no longer than was necessary to insure accurate and con- 

 cordant results. In an artificial digestion the accumulation of the pro- 

 ducts formed tends to retard the action of the fluid, but in no case were 

 our results impaired by saturation of the digestive mixture, for that 

 this could never have occurred ordinarily is plainly shown by the large 

 amount of blood fibrin dissolved by the gastric juice in a trial experi- 

 ment. The addition of larger amounts of flesh, moreover, in the case 

 of fish, 30 to 40 grams, simply diminished the digestive action. 



' Determined by simply drying at 100° C. until of constant weight. 



