. IM/DO-A CIDS FORMED IN TR J 'I 3 TIC DIGESTION. 425 
during which time most of both the leucine and tyrosine crystallises out. After 
separation of the crystals, the filtrate may be once more reduced in bulk by 
evaporation and a second crop of crystals obtained as before. 
To the syrupy mother-liquor now remaining absolute alcohol is added, until 
precipitation of the peptone commences, when the addition of alcohol is 
stopped and the precipitate of peptone redissolved by gently wanning. The 
solution is now set aside to cool and crystallise as before. The united crops of 
crystals of mixed leucine and tyrosine are boiled with alcohol, which dissolves 
the leucine and but little of the tyrosine. On concentrating this alcoholic extract, 
leucine crystallises out and may be purified by recrystallisation from alcohol. 
From the residue insoluble in alcohol the tyrosine is obtained by dissolving in 
weak ammonia water and neutralising. 
The yield, both of leucine and tyrosine, obtained from different materials 
varies greatly, but in all cases the former is always formed in much larger 
quantity. The following table l gives the percentage yield of the substances 
obtained in some cases ; the figures indicate parts per 100 : — 
Source. 
Leucine. 
Tyrosine. 
Observers and Method. 
Gelatine . 
T5-2 (a) 
Xone (a) 
(a) Nencki, boiling with dilute 
sulphuric acid. 
Ligamentura nuchae 
36-45 (b) 
0-25 (6) 
(b) Erlenmeyera.uASch'6ffer, boil- 
ing for some hours 1 pint of 
material, 2 pints sulphuric 
acid, 3 pints water. 
Fibrin 
14-0 (b) 
2-0 (6)-3-3 (c) 
(c) Hlasiwetz and Habermann, 
heating with bromine un- 
der pressure. 
Muscle . 
1S-0 (b) 
1 -o (b) 
(d) Stadelcr, heating with sul- 
phuric acid. 
Horn 
10-0 (b) 
3-6 (70-4-0 (d) 
(e) Schutzenberger, heating with 
baryta water for four to six 
days, at 16(T-200 = C. 
Egg albumin . 
•22-6 (c) 
1-0 (b)-2-0(c) 
Plant albumin 
17-3 (c) 
2-0 (e) 
Casein 
19-1 (c) 
4-1 (e) 
Fibrin 
7-9 (/) 
3"3 (/) 
(/) Kiihne, digestion of boiled 
fibrin. 
Aspartic acid, or amido-succinie acid [C 2 H 3 .(XH.,).(COOH).,], does not 
occur in any of the animal tissues or secretions, but is formed in small 
quantity in all those decompositions of proteids and their allies already described 
as furnishing leucine and tyrosine. 2 It was first identified among the products 
of pancreatic digestion of fibrin by Eadziejewski and Salkowski, 3 and von 
Knieriem afterwards showed that it is also formed in the pancreatic digestion 
of plant glutin. 
It may also be obtained by decomposing asparagin (amido-succinamic acid) 
by an alkali or acid, thus : — 
CH 9 — CO OH 
I " 
CH(XH 2 )— CO(XH 2 ) + HC1 + H 2 
(asparagin or amido-succinamic acid). 
CH — COOH 
+ XH 4 C1. 
CH(XH 2 )— COOH 
(aspartic acid or amido-succinic acid). 
1 Compiled from Maly, Hermann's "Handbuch," Bd. v. (2), S. 209 et seq. 
- Piitthausen and Kreuster, Journ. f. pralct. Chem., Leipzig, 1871, Bd. iii. S. 314 ; 
Hlasiwetz and Habermann, Ann. d. Chem., Leipzig, 1S71, Bd. clix. S. 304. 
3 Eadziejewski and E. Salkowski, Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, Bd. vii. 
S. 1050 ; Ann. d. Chem., Leipzig, 1S73, Bd. clxix. S. 150 : W. v. Knieriem, Ztschr. f. Biol., 
MUncheu, 1S75, Bd. xi. S. 198. From 100 pts. of dry egg albumin Hlasiwetz and 
Habermann obtained 23*8 pts. of aspartic acid by the action of bromine in sealed tubes. 
