382 
Journal of Agricultural Research 
Vol. XXIX, No. S' 
from 1,500-2,400 gm. gross body 
weight. 
Y represents the weight of the liver 
in grams and X represents the gross 
body weight in grams. 
The percentage weights of the liver 
form a curve also resembling the per¬ 
centage curves for the other parts of 
the digestive system, although the 
changes are not so marked. There is a 
short period of initial rise from 3.1 per 
cent at hatching to a maximum of 6.2 
per cent at 7 days, followed by a slow 
decline to about 2.5 per cent. There 
seems to be a tendency for the liver in 
the females to run higher (possibly 1 
per cent higher) than in the males. 
This is reversed for the six older 
fact made on the record cards.) The 
storage of additional fat, glycogen, 
etc., in the heavy livers is a possible 
explanation for the marked increase in 
the weight of the liver in the last three 
cases on the chart and for at least some 
of the heavier cases recorded for 
chickens under 2,400 gm. In the very 
young chicks the liver had a yellowish 
color, but on the fourth day the liver 
was pinkish, and from then on rapidly 
changed to the characteristic dark red 
in the older birds. 
Zaitschek (31) reports no appreciable 
change in the percentage values of the 
livers in two chickens which he fat¬ 
tened for 55 days. At the end of the 
period they had gained 71.9 and 133.8 
Fig. 17.—The percentage weight (lighter line) and the weight in grams (heavier line) of the liver. The 
three cases above 2,400 gm. gross body weight are shown on the chart though not included in the com¬ 
putation of the formulas 
chickens, for in these the percentage 
weights of the livers in the males aver¬ 
age higher than in the females. After 
the chickens become mature, they 
become very fat, especially the females. 
In some of these older fat chickens the 
liver had a yellowish color, and these 
are the heavier specimens in Figure 17. 
For example, the last three cases (not 
included in the curve) were adults 
which were very fat and had the 
yellowish-colored livers. The female 
at 1,640 gm. had a yellow liver, also the 
females at 1,520 and 1,550 gm. The 
male at 1,600 and the female at 1,840 
gm. also have heavy livers, but these 
livers were not specifically observed to 
be yellowish in color. (They may 
have been so, with no mention of the 
per cent of the initial gross body weight 
and yet their livers formed/ respec¬ 
tively, 2.3 and 3 per cent of the live 
weight. The range in percentage weights 
of the liver in the 131 specimens reported 
by him was from 1.4 to 4.7 per cent. 
Welcker and Brandt (28) give 1.88 
per cent as the average percentage 
weight for the liver in two male fowls, 
which is lighter than that found in the 
present series. They record a varia¬ 
tion from 1.68 to 4.74 per cent for the 
various other species of birds. The 
liver of the chicken is lighter than that 
of the rat as given by Jackson (8). He 
finds it forming 4.7 per cent at birth, 
increasing to nearly 8 per cent at 3 
weeks, later decreasing to about 4.5 
per cent in the adult. 
