Jan. 10, 1916 
Mature Beef and Immature Veal 
687 
digestion of a protein by pepsin-hydrochloricacid solution is the combination of the 
protein and the acid to form a class of substances known as acid proteinates. These 
are soluble in dilute acids and alkalies, but are insoluble in water. 
The filtrates obtained at the end of the digestion period contained (1) the acid 
proteinates and (2) the next cleavage products of the acid proteinate, the proteoses 
and peptones. A measured amount of filtrate, generally between 50 and 80 c. c., 
taken before the washing of the residue was begun, was nearly neutralized with IV/5 
sodium hydroxid. The exact amount added varied in the different experiments; 
calculated to 100 c. c. of filtrate it varied around 21 c. c. The 100 c. c. of 0.2 per cent 
hydrochloric acid in which the digestions were made were equivalent to 28 c. c. of 
approximately iV/5 sodium hydroxid. The addition of alkali was stopped when a 
flocculent precipitate of acid proteinate was thrown down. The mixture was then 
rapidly brought to a boil and filtered on a weighed paper. This was dried along with 
the undigested residues, and the results calculated in the same way. 
The difficulties involved in promptly checking the action of the pepsin at the end 
of the digestion period were very apparent to Crindley, Mojonnier, and Porter (1907, 
p. 68), who after many trials found that the addition of formaldehyde solution to a 
digestion mixture brought the digestion to a close. Differences in length of time 
required for filtration will not then involve the error previously mentioned. This 
method, however, is not the only one. By using small amounts of pepsin the digestion 
period may be made long; and then it makes little difference whether a particular 
mixture requires a few more or a few less hours to filter completely. An objection 
to this procedure is that the acid alone in the control may digest as much as the acid 
plus the small amount of pepsin, and the action of the pepsin under such conditions 
can not be measured with certainty. Further, the amount of pepsin must not be 
large enough to permit the digestive processes to go to completion, for the undigested 
residue then obtained represents material not digestible under the conditions, and 
no information is obtained regarding the rate at which digestion took place. If 
allowed time enough, both a fast horse and a slow horse will be found at the same 
place at the end of a race. In experiment 13, Table VIII, the undigested residues 
obtained after long digestion with fairly large amounts of pepsin represented the 
amount of meat constituents not digestible by the pepsin-hydrochloric-acid solution. 
No information as to whether the beef or the veal digested faster could be obtained 
from such data. That the residues in this experiment were almost certainly fat is 
indicated by the results of Table IX, with which experiment 13 is comparable because 
the concentration of pepsin was the same in both—i. e., 10 mgm. to 100 c. c. of 0.2 
per cent hydrochloric acid. Under these conditions practically all of the nitrogen in 
the beef and veal went into solution in 24 hours, leaving the fat, which is not digested 
by pepsin-hydrochloric-acid solution. Fat determinations were not made. Accord¬ 
ing to Fish (1911, p. 132), beef contains more fat than ordinary veal. This is proba¬ 
bly still more true of immature veal. The larger residues from beef in experiment 
13 are in accord with the data of Fish. 
