102 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
proportion of it being removed by boiling for 2 hours and also by digestion at 40° C. 
for a day with 0.1 per cent HC1. In the former case, however, the collogen is very 
firmly combined and is dissolved only by long-continued boiling (30 to 40 hours), and 
is much less affected by dilute acid digestion. Whether this is due to an essential 
difference in the nature of the collogen itself or to a difference in the chemical com- 
bination of it with other constituents of the scale is a subject now under investigation. 
UTILIZATION OF THE COLLOGEN. 
Some experiments relating to the use of the large amount of collogen present in 
fish scales were made tentatively. Menhaden scales were used, as these fish are now 
utilized in immense quantities in fertilizer works, and the removal and use of their 
scales, if possible, could be made at least expense. The scales can be readily removed 
from menhaden — more readily, indeed, than in the case of most fish. 
Analyses were made to determine the amount of the collogen in the scales, both 
when dried at 150° C. to constant weight and when only air- dried. Also the scales from 
an average-sized specimen were removed and weighed to get data for determining 
the amount of gelatin which large quantities of moist fish would yield. 
The scales from one menhaden (one-half hour after removal from the water and 
weighing 155 grams) were removed, washed, and thoroughly scrubbed to remove 
adhering tissue and then dried in the air at 20° C. 
The scales, air-dried, weighed 6.9565 grams; dried to constant weight at 105° C. 
they weighed 5.5215 grams. The moisture in the air-dried scales then is 20.58 per 
cent, and the fish thus yielded 1.26 per cent scales, air-dried, or 1.004 per cent scales 
dried at 105° C. ; that is, an average moist menhaden yields 1 per cent of its weight 
in anhydrous scales. One ton of fish would yield 20 pounds of dry scales. 
The scales from several specimens were removed, cleaned, and dried in the air, 
and then to constant weight at 105° C. ; 3.8180 grams of these scales were ignited and 
gave 1.5679 grams of ash, or 41.07 per cent ash. The organic matter by difference 
was 58.93 per cent. As shown above, the dry organic matter of menhaden scales 
contained 23.74 per cent of ichthylepidin and 76.26 per cent of collogen. Hence 
the following protocol: 
Scales. 
Air-dried. 
Dried at 105° C. 
P.ct. 
20. 58 
P.ct. 
00. 00 
32. 61 
41.07 
Organic matter 
(Ichthylepidin, 11.11. 
46. 801 
(Ichthylepidin, 13.99. 
58. 93 ■> 
(Collogen, 44.94. 
(Collogen, 36.69. 
1.26 scales. 
1. 00 scales. 
Thus a ton of menhaden should yield nearly 10£ pounds of pure scale-gelatin (16 
per cent moisture, as in the usual commercial article). As Morner has shown this 
gelatin to be remarkably pure, containing only about 0.1 per cent ash, it should 
command, when properly prepared, a high commercial value. 
Brown University, Providence , Rhode Island. 
