32 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 
2. Treatment uritJi acids. — Prolonged heating of proteids with dilute 
acids results in their hydration and the formation of proteoses and 
peptone. 1 Strong acids produce the same effect at the ordinary tempera- 
ture in the course of a few days.' 2 This method has the disadvantage 
that strongly coloured materials make their appearance, and to avoid 
this Hlasiwetz and Habermann 3 introduced the important modification 
of heating with strong hydrochloric acid and stannous chloride, by which 
pale yellow solutions were obtained without a trace of charring. A 
certain amount of reduction occurred during the operations, leading to 
the formation of stannic chloride. These methods yielded the following 
substances : — 
(1) Ammonia ; (2) an amido-acid of the acetic series, namely, leucine ; 
(3) two amido-acids of the acrylic series, namely, asparaginic acid 
(C 4 H 7 N0 4J amido-succinic acid), and glutaminic acid (C 5 H 9 N0 4 , amido- 
pyrotartaric acid), both in considerable amount; (4) tyrosine or 
oxyphenylalanine. 
Ritthausen 4 was the first to separate glutaminic acid and asparaginic acids 
from proteids. He and Kreusler suggested that glutaminic acid was a typical 
product of vegetable proteid ; but Hlasiwetz and Habermann 5 obtained it from 
casein, albumin, and other animal proteids. The glutaminic acid they isolated 
was levorotatory, while that obtained by Schiitzenberger was only found in 
small quantities and was optically inactive. By boiling the active form with 
barium hydrate, however, it is converted into the inactive form, and further, 
the inactive form if allowed to ferment under the action of the mould 
Penicillium glaucum, is transformed into the optically active modification. 6 
Employing the same method, Horbaczewski 7 obtained leucine, glutaminic acid, 
and glycocine from gelatin, but no asparaginic acid or tyrosine. Hofmeister, s 
however, obtained small quantities of asparaginic acid. 
Fromelastin were obtained ammonia, leucine, tyrosine, glycocine, butalanine 
(C 5 H n NO.„ amido-valeric acid), but no glutaminic or asparaginic acids. 9 
From reticulin (a substance separated from reticular tissue) were obtained 
ammonia, sulphuretted hydrogen, and amido-valeric acid, but no tyrosine or 
glutaminic acid (Siegfried). 
By the employment of the same method, Drechsel 10 has discovered two 
new substances, which are of special interest. He began by studying 
the quantities of nitrogenous bodies which other observers had obtained ; 
and if he assumed that only one-half of these had been isolated there 
still remained about 30 per cent, of the nitrogen of the proteid to be 
accounted for. He pointed out also that Schiitzenberger obtained 
carbonic anhydride by his method, and that Hlasiwetz and Habermann 
did not by theirs. He argued from this that there should be some other 
1 Xeumeister, Ztschr. f. Biol., Munch en, Bd. xxiii. S. 3S1. 
2 See Brodie, Science Progress, London, 1895, vol. iv. p. 67. 
3 Ami. d. Chcm., Leipzig, 1873, Bd. clxix. S. 150. In a paper published previous to 
this by the same observers {ibid., Bd. clix. S. 30-1), they sought unsuccessfully to estahlish a 
definite relationship between proteids and carbohydrates. 
4 Journ. f. prakt. Ghem., Leipzig, Bde. xeix. S. 454 ; cvii. S. 218. 
5 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1872, Bd. ix. S. 114. 
6 Ber. d. dcutsch. chem. Gesellsch., Berlin, Bd. xvii. S. 388. Similar changes in the 
optical varieties of leucine and other substances are similarly produced. 
7 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1880, Abth. 2, Bd. Ixxx. S. 101. 
8 Ztschr. f. physiol. CJiem., Strassburg, Bd. ii. S. 299. 
9 Horbaczewski, Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1886, Abth. 2, Bd. xcii. 
S. 657. 
10 "Der Abbau d. Eiweissstoffe," Arch. f. Physiol., Leipzig, 1891, S. 248. 
