690 
Journal of Agricultural Research 
Vol. V, No. 15 
veal calves were compared with an almost equal number of samples of market veal and 
beef, using “3.35 milligrams of scale pepsin” in 100 c. c. of 0.2 per cent hydrochloric 
acid. Fish (p. 52-53) concludes this part of the work with the following statement: 
The results show that, as regards the averages, the differences in the digestibility of 
the tissues of bob veal and market veal are so slight as to be negligible; but such as they 
are, they are slightly in favor of the bob veal as a whole. The differences between the 
beef and veal is [sic] more noticeable, but the apparent greater digestibility of the 
veal may be due in part to the fact that as a rule there is a slightly smaller percentage 
of water present in the beef as weil as a somewhat greater amount of connective tissue. 
As the greatest difference shown by the averages is but 3 per cent under the condi¬ 
tions of the experiments, it would indicate no serious difficulties in the digestibility 
of any of the material. 
A redeeming feature of the method used in experiments 1 to 13 is its simplicity, 
both in the technic used and the equipment required. That the results obtained are 
substantially correct is indicated by the fact that repetitions of the measurements, 
using different methods, involving different errors, yielded similar results. 
second method: measuring the rate of formation of proteose, peptone, 
AND AMINO-ACID NITROGEN 
Into each of two 2-liter Jena Erlenmeyer flasks 100 gm. of freshly hashed beef were 
weighed to the 0.1 gm. Similar portions of veal were weighed into two similar flasks. 
After adding 750 c. c. of water to each flask and stirring, the flasks were kept in a boil¬ 
ing-water bath for one hour. They were then cooled, weighed, and the evaporated 
water replaced. The stoppered flasks remained in cold storage overnight. Two of 
these, one of beef and one of veal, were used for the determination of extractive 
nitrogen as already described on p. 673. The next morning the flask containing 
the beef and the flask containing the veal for the digestion experiment were quickly 
warmed to 40 0 C. The dry, powdered enzym was then added, followed by 1 liter of 
0.4 per cent hydrochloric acid or of 1 per cent sodium-carbonate solution. Water 
was then added to bring the final volume up to 2,000 c. c. In this way every diges¬ 
tion experiment was begun with 100 gm. of beef or veal, plus 2,000 c. c. of 0.2 per 
cent hydrochloric acid when pepsin was used (see Table IX), or 2,000 c. c. of 0.5 per 
cent sodium carbonate when trypsin was used (see Table X). During the course of 
the digestion the flasks were kept in a 40 0 C. water bath, except when they were 
removed to mix their contents or to take samples for analysis. The treatment of the 
digestion mixtures containing pepsin-hydrochloric-acid solution and those containing 
trypsin-sodium carbonate solution will be described separately. 
Digestion in pepsin-hydrocheoric-acid solution. —During the earlier part of 
the experiment the contents of the flasks were mixed about every 15 minutes. Later, 
when most of the meat had gone into solution, the mixing was done at longer intervals, 
but always the same for both flasks. In the experiments summarized in Table IX the 
rate of digestion was measured at the time intervals there indicated by removing 
100 c. c. portions of supernatant digestion fluid and determining in this the amount 
of nitrogen present as acid proteinate, proteoses, and peptones. By difference the 
nitrogen in the undigested residue could be obtained. If, for example, it was desired 
to obtain data on veal for one hour’s digestion, the veal mixture was well mixed 45 
minutes after the digestion was begun and was allowed to remain in the water bath 
for 10 minutes, in order to allow meat particles to settle to the bottom of the flask. 
The flask was then removed from the bath, and with a calibrated 100 c. c. pipette 100 
c. c. of the supernatant suspension was transferred to a 200 c. c. Erlenmeyer flask. 
Exactly 60 minutes after the digestion began, the action of the pepsin-hydrochloric- 
acid solution was stopped by nearly neutralizing the contents of the 200 c. c. Erlen¬ 
meyer flask by the addition of iV/5 sodium hydroxid and bringing it to a boil by heat¬ 
ing directly over a Bunsen burner. The flask containing the digestion mixture was 
