Contributions from the Biological Laboratory of the U. S. Fish Commission, 
Woods Hole, Massachusetts. 
THE ORGANIC CONSTITUENTS OF THE SCALES OF FISH. 
By E. H. GREEN and R. W. TOWER. 
Morner 1 has shown that the scales of many species of fish contain, in addition 
to mineral matter and collogen, a peculiar albuminoid. To this albuminoid he gave 
the name ichthylepidin. Previous observers had overlooked this substance and had 
considered that the organic matter in tish scales consisted wholly of collogen. The 
present study was undertaken to determine how widely ichthylepidin is distributed 
in the scales of the common American fishes. 
Morner prepared his ichthylepidin in the following way: The clean scales were 
digested at room temperature with a large excess of 0.5 per cent hydrochloric acid, 
0.05 per cent caustic potash, and 0.01 per cent acetic acid. Each digestion extended 
over several days. This treatment removed soluble proteids, most of the guanin, 
the chrondroitin-sulphuric acid, and the inorganic matter. The residual scales were 
then digested with 0.1 per cent hydrochloric acid at 10° C. The residue thus freed 
from collogen was washed with alcohol and ether, and dried. The substance so 
obtained (pure ichthylepidin) was insoluble in boiling water, in cold dilute acids, and 
in alkalies; but it was soluble in hot solutions both of dilute acids and alkalies, and 
in the cold concentrated solutions of the same. It gave a strong Millon’s reaction 
and contained much loosely combined sulphur (as shown by the blackening of the 
substance when boiled with an alkaline solution of lead acetate). By the two latter 
reactions the presence of ichthylepidin may, according to Morner, be determined in 
i fish scales. 2 
Morner examined the scales of 12 species of fish, all of which showed the presence 
of ichthylepidin; in the ganoid scales of the American gar-pike ( Lepisosteus osseus), 
however, he found no trace of it. 
In the course of our work we have studied 10 species of American fish repre- 
senting 25 families. In every case the scales were taken from fresh, healthy fish, and, 
!Zeit. f. phys. Chemie, 1898, vol. 24, p. 125. 
-Morner, op. cit. , p. 136: “Wenn man untersuchen will, ob die Sehuppen einer Fisehart ichthylepidinhaltig sind 
Oder nicht, geniigt es, sie nach vorgangiger Bntkalkung durch Kochen, theils mit Millonschen Reagens, theils mit 
alkalischer Bleilosung zu priifen; wenn dabei tief dunkelrothe Farbung, resp. Schwarzfarbung ausbleibt, ist die 
' Gegenwart des ichthylepidins ausgeschlossen.” 
F. C. B. 1901—7 
97 
