322 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
grams of the finely divided and well-washed tissue were boiled for 6 hours in half a 
liter of distilled water, the water being renewed as it evaporated. The tissue almost 
completely dissolved, and the yellowish solution on cooling became somewhat viscid, 
but it did not gelatinize, even when evaporated to a volume of only 100 c. c. Tbe 
concentrated solution was diluted and filtered. It was neutral to litmus, was precipi- 
tated by phosphotungstic acid, and by phosphoinolybdic acid; the precipitates were 
insoluble on heating, but were soluble in potassic hydrate. When precipitated by 
Milieu’s reagent the precipitate was soluble in excess of reagent. When precipitated 
by tannic acid, by metaphosphoric acid, absolute alcohol, and mercuric chloride in 
presence of free hydrochloric acid the precipitates were insoluble. 
The solution gave no precipitate with acetic acid and potassium ferrocyanide, 
neutral or basic acetate of lead, alum, cupric sulphate or acetate, ferric chloride, 
sodium orthophosphate, or mercuric potassium iodide. It was not blackened when 
boiled Avith lead acetate and potassic hydrate. It gave a strong biuret reaction, and 
on boiling did not reduce copper. Hot concentrated sulphuric acid and glacial acetic 
acid produced no violet coloration. Hot strong nitric acid gave no precipitate or color- 
ation, but subsequent addition of ammonia caused a deep orange tint. Saturated 
with ammonium sulphate, the solution gave a copious precipitate, which floated on the 
surface of the liquid, forming a coagulum-like layer. Picric acid in saturated solution 
produced a light-yellow precipitate, insoluble in excess of the reagent, soluble in hot, 
insoluble in cold ivater. On shaking, a stiff coagulum formed above the subnataut clear 
liquid, so that the test tube could be inverted without loss of its contents.' 
To a feiv centimeters of the original solution, several drops of formaldehyde (40 
per cent solution in Avater) AA r ere added, and the Avliole evaporated to dryness. The 
residue was insoluble in hot or cold water. It had become apparently formogelatin. 
The reactions given above shoAv that true proteids, also chondrin, are absent, or 
present in quantities too small for detection. All the phenomena, especially the 
peculiar and characteristic reactions given by picric acid, ammonium sulphate, and 
formaldehyde, point to the presence of gelatin, notwithstanding the fact that the 
solution did not gelatinize and that the original tissue was soluble in dilute potassic 
hydrate. Elastin can be present oidy in traces, if at all, since it is insoluble in boding 
Abater, even after 90 hours’ boiling, 1 2 and insoluble also ini per cent potassic hydrate, 3 
which dissolves the tissue under consideration. 
The following experiments were made to determine whether other substances 
Avere present with the collogen-like albuminoid. 
Several grams of the alcoholic tissue were cut up, Abashed, and treated with cold 5 
per cent potassic hydrate. After 124 hours the tissue Avas almost wholly dissolved; the 
solution Avas filtered, slightly acidified with acetic acid, and submitted to the following 
reactions. Phosphotungstic acid gave a precipitate soluble on heating, and phospho- 
molybdic acid, tannic acid, and metaphosphoric acid also gave precipitates. The 
solution aa 7 as not precipitated by acetic acid and potassium ferrocyanide, nitric acid, 
basic or neutral lead acetate, or copper sulphate, and it gave a strong biuret reaction. 
There was no coloration with hot sulphuric and glacial acetic acid. The fact that the 
precipitate given by phosphotungstic acid is soluble by heating shows, according to 
the researches of Mallet, 4 that true proteid substances can not be present in the 
1 Allen and Tankard’s test for gelatin. Allen’s Com. Organ. Analysis, vol. iv, 1898, p. 469. 
-Chittenden and Hart. Zeit. fur Biologic, 7 Bd., s. 369 — (abs. — Horbaczewski Zeit. fiir Phys. 
Chemie, Bd. 6, s. 330.) 
s Ibid. 
4 U. S. Dept. Agric., Di\ r ision of Chem., Bull. 54, 1898, pp. 20-21. 
