Jan. io, 1916 
Mature Beef and Immature Veal 
689 
A second method of checking the action of the pepsin-hydrocloric-acid solution used 
in experiments 8,10, and 12 involved nothing more than the neutralization of the diges¬ 
tion mixture at the end of the desired time. Pepsin digests in the presence of free acid; 
it does not act in neutral solutions with any appreciable speed. Thus in experiment 
10, and in experiment 12, which was a repetition of experiment 10, exactly four hours 
after the digestion was begun by adding the pepsin solution to 5-gm. portions of meat 
suspended in 100 c. c. portions of 0.2 per cent hydrochloric acid, the entire mixture 
was neutralized by the addition of2ito25C.c.of Nj 5 sodium hydroxid. This checked 
the peptic action at once, but also precipitated the acid proteinate. The mixture was 
then quickly brought to a boil, after which filtration, whether fast or slow, may be 
continued at the convenience of the worker. Obviously the residue in this case does 
not give as detailed information as that obtained by filtration of undigested residue 
and precipitation of acid proteinate in the filtrate. In experiments 10 and 12 the veal 
digested a little faster than the beef. 
In experiments 5 to 8, practically fat-free beef and veal, prepared as described on 
page 685, were used. The object was to eliminate the error due to the fat, which, when 
present, is weighed with the undigested protein. One-gm. portions of the dry powders 
were used instead of the 5-gm. portions of fresh meat. Otherwise the procedure was 
the same as in the other experiments, except that, in so far as the proteins present 
had already been coagulated by exposure to alcohol, ether, and a temperature of 85° C. „ 
heating the mixture of meat powder and water in a boiling-water bath was omitted. 
The results in experiment 5 were invalidated by molds. In experiments 6 to 8 the 
results indicate a slightly more rapid digestion of beef sample x.i. 
The most interesting results in Table VIII are those of experiments 1,2, and 6. In 
experiment 1 so minute a quantity of pepsin as 0.01 mgm. in 100 c. c. of 0.2 per cent 
hydrochloric acid exerted an equally distinct digestive action on both the beef and 
veal. With 0.1 mgm. of pepsin the digestion was unmistakable, indicating that in 
these particular cases the immature veal was as susceptible to the action of minute 
amounts of pepsin as the mature beef. To ascertain whether this was true or not was 
the object of experiments 1 and 2. 
It will be noticed that in the experiments summarized in the table the amounts 
of pepsin used varied from 0.01 mgm. to 1,000 times this amount—i. e., 10.0 mgm. A 
wide range of enzym concentration in such work is not only desirable but almost 
necessary. What is true at one concentration of enzym may not be true at another 
very different one. Thus, Berg and Gies (1907) found that in acetic acid fibrin would 
digest very slowly when the amount of pepsin present was comparatively small, but 
in the presence of large amounts of this enzym digestion proceeded with a wholly 
unexpected speed. 
A comparison of the results for beef in Table VIII with some of the data obtained 
by Grindley, Mojonnier, and Porter (1907, p. 66) in their artificial-digestion experi¬ 
ments can not very well be made. These investigators used 250 mgm. of pepsin per 
100 c. c. of 0.33 per cent hydrochloric acid. The kind of pepsin preparation used was 
not stated, but, assuming it to be the usual 1 to 3,000 product, their digestion mixtures 
contained 25 times as much pepsin as the strongest digestion mixtures mentioned in 
Tables VIII or IX. Their conditions of comparatively high pepsin and high acid 
concentration probably were not favorable for the detection of small differences in 
digestibility, although these conditions may have been desirable for other reasons. 
Perhaps the only work with which the data of Table VIII can be compared are the 
recent results obtained by Fish (1914) on the comparative digestibility of beef, market 
veal, and immature veal. In the absence of a statement pertaining to the treatment 
of the meats, the inference may perhaps be drawn that the digestion experiments were 
made on raw meats. Otherwise, the general method and conditions of Fish’s digestion 
experiments were similar to those in experiments 1 to 13. Samples from 22 immature 
17209°—16-3 
