of Sugar in the Liver, in the presence of Peptones. 185 
The 14 ¢. c. should have contained 0°2414 gram dextrose, the equiy- 
alent of 0°2146 gram of glycogen. 
B. 0°6190 gram glycogen dissolved in 100 ¢. c. of water was heated 
at 100° C. for 17 hours in the presence of 2 per cent. of hydrochloric 
acid. Solution was then neutralized, evaporated and made up to 50 ¢.c. 
18 c.c. gave 0°4585 eram Cu=0°2470 gram dextrose==0°2223 gram glycogen. 
VST e860) 045555 4 Cn 0-2454 a =0-2208 Y 
The 18 c. c. should have contained 0°2475 gram dextrose, equal to 
0°2228 gram of glycogen. Hence, it is seen that 17 hours heating at 
100° C. is needed for a complete conversion of glycogen into dextrose, 
which was the time invariably employed in the after experiments. 
Influence of peptone on the conversion of glycogen into sugar by 2 
per cent. HCl at 100° C.—The question naturally suggested itself in 
this connection whether the presence of peptone would interfere in 
any way with the complete conversion of glycogen into dextrose or 
whether the peptones by this long heating at 100° C. with the acid, . 
would undergo’ any change by which reducing bodies might be 
formed and thus endanger the accuracy of the results. The latter 
point was tested by heating 2 grams of peptones in 100 e. ¢. of water 
containing 2 per cent. of hydrochloric acid for 17 hours at 100° C., 
at the end of which time no reduction at all could be obtained with 
Fehling’s solution. 
The first point was tested by the following experiment: 
0°9290 gram of pure glycogen was dissolved in 100 ¢. ¢. of water, 
then 2 grams of peptone were added and sufficient acid for the solu- 
tion to contain exactly 2 per cent. HCl, after which the mixture was 
heated at 100° C. for 17 hours. The solution was then neutralized, 
brought to a volume of 100 ¢. c. and the sugar determined. 
10 ec. c. gave 0°1985 gram Cu=0'1017 gram dextrose=0°0915 gram glycogen, 
10S 80-2025“ Cu—0°1039 i =0°0934 = 
whereas in the 10 ¢. c. then should be present, according to calcu- 
lation 071032 gram dextrose, the equivalent of 0°0929 gram of 
glycogen. Consequently the presence of peptone does not interfere 
with the accurate determination of glycogen by this method. 
Influence of the presence of peptone on the determination of sugar 
by Allihn’s method.—Seegen* finds that the volumetric determina- 
tion of sugar with Fehling’s solution is not materially affected by 
the presence of peptone. By repeated experiments we have con- 
vinced ourselves, that in the use of the gravimetric method, the 
* Pfliiger’s Archiv, vol. xxviii, p. 115. 
TRANS. Conn. ACAD., Vou. VII. 24 Nov., 1885. 
