The average amount of hydrochloric acid, however, is approximately 0.2 per cent., while to the pepsin no definite figure can be given, since as yet the chemist has not been able to isolate the ferment in a pure state. Further, it is quite certain that both ferment and acid are subject to great variation in the amount present in the secretion at different stages of digestion and under different conditions of health and nutrition. In view of these facts we have experimented under varying conditions in order that our results may have as wide an application as possible. The methods pursued were as follows: (a) With fluid egg-albumin.1 The albumin solution was prepared after the method recommended by Schütz. A quantity of undiluted white of egg was freed from globulin by the addition of hydrochloric acid of specific gravity 1.12 (4.2 c. c. acid to 300 c. c. of albumin), the mixture shaken vigorously, and after standing some hours filtered through paper. The clear acid fluid was then made exactly neutral with dilute sodium carbonate, after which it is ready for use. Ten c. c. of this fluid contain a little less than one gram of coagulable proteid, the exact amount being determined by heat-precipitation, collecting the coagulum on a weighed filter and drying at 110° C. The digestive experiments were made in series, each individual mixture containing the same volume of the prepared albumin solution (10-20 c. c.), together with the same amount of pepsin and acid. The albumin solution was introduced into a small flask of 200 c. c. capacity provided with a suitable stopper, water and alcohol, or alcoholic fluid, being added to make the volume up to 50 c. c. Lastly, 50 c. c. of 0.4 per cent. hydrochloric acid, containing a known amount of pepsin, were added, making the total volume of each mixture 100 c. c., and the strength of acid 0.2 per cent. HCl. It is thus evident that the only variable element in the mixtures of a given series is the amount of alcohol or alcoholic fluid present. The flasks were then placed in a water-bath, kept approximately at the body temperature (3840° C.) for a definite period- usually five to seven hours. At 1 See R. H. Chittenden, "Observations on the Digestive Ferments," Medical News, Philadelphia, February 16, 1889. 2 Zeitschr. f. physiol. Chem., ix. 581. the end of the allotted time, the extent of digestive action was determined by simply heating the mixtures to boiling, neutralizing the acid fluid by addition of an equivalent amount of sodium carbonate in a one per cent. solution, and collecting the precipitate of unaltered albumin or acid-albumin on a weighed filter, washing it with boiling water until free from chlorides, and then drying at 110° C. until of constant weight. The difference between the weight of coagulable albumin introduced and the amount found at the end of the experiment gives the amount of soluble digestive products, i. e., albumoses and peptones, formed under the conditions of the experiment. In this way it is possible to measure accurately the extent of proteolytic action under varying conditions. (b) With coagulated blood-fibrin. Fresh blood-fibrin from the blood of oxen or sheep was washed with water until quite white, then boiled repeatedly with water, after which it was thoroughly extracted with cold alcohol, boiling alcohol, and, lastly, with ether. It was then ground to a coarse powder and passed through a sieve, so constructed that the particles collected were all approximately of the same size. The so prepared powder was then dried at 110° C. until of constant weight. The digestive experiments with this form of proteid matter were conducted as follows: A definite amount of alcohol or alcoholic fluid was introduced into each flask, water being added to make the volume 50 c. c. Then 50 c. c. of 0.4 per cent. hydrochloric acid containing a known amount of pepsin were added, thus making the total volume of fluid 100 c. c. To this mixture. two grams of the prepared fibrin were added. Thus, as in the experiments with fluid egg-albumin, all of the mixtures of a given series were exactly alike in containing the same volume of 0.2 per cent. hydrochloric acid, the same amount of pepsin, etc., but unlike in the percentage of alcohol or alcoholic fluid present. For comparison, one mixture of each series contained no alcohol whatever. When prepared, the mixtures of a given series were placed in a bath at 38°-40° C. for two to three hours, where they were kept under exactly the same conditions, being stirred or shaken to the same extent, etc. At the end of the given period the mixtures were heated to boiling to destroy the ferment, after which the undigested residue was collected on a weighed filter, washed with boiling water until free from all soluble matter, then dried at 110° C. until of constant weight. The difference between the weight of the fibrin taken and the undissolved residue is a true measure of the digestive action under the conditions of the experiment. Action of Absolute Alcohol (99.5-100 per cent.). The percentages of alcohol referred to are percentages by volume unless otherwise specified. The pepsin employed was a very active scale pepsin marked 1: 4000. Conditions: Experiment 1. Proteid fluid egg-albumin (20 c. c.). 20 c. c. albumin solution contain 1.6398 grams dry albumin. Period of digestion 611 hours at 38°-40° C. Proteid fluid egg-albumin (15 c. c.). 15 c. c. albumin solution contain 1.0522 grams dry albumin. Period of digestion 5 hours at 38°-40° C. Proteid fluid egg-albumin (10 c. c.). 10 c. c. albumin solution contain 0.8199 gram dry albumin. Period of digestion 5 hours at 38°-40° C. 1 Expressing the relative extent of digestive action as compared with the action of the control experiment, the latter being taken as 100. Proteid fluid egg-albumin (20 c. c.). 20 c. c. albumin solution contain 1.9198 grams dry albumin. Period of digestion 5 hours at 38°-40° C. Proteid blood-fibrin (2 grams). 0.016 gram pepsin; 0.2 per cent. hydrochloric acid. Period of digestion 24 hours at 38°-40° C. The following five series of experiments were all made after the same plan, each mixture containing 2 grams of blood-fibrin, 0.016 gram pepsin in 0.2 per cent. hydrochloric acid, and warmed at 38°-40° C. for 24 hours: 1 Filtered very slowly and could not be washed thoroughly; hence, the result is only approximately correct. In the following three experiments the conditions were the same as in the preceding, excepting that the mixtures were warmed at 38°-40° C. for 2 hours instead of 24 hours: In the following three experiments the conditions were the same as in the preceding, except that the mixtures were warmed at 38°-40° C. for 12 hours: |