Oct. 15, 1924 
Postnatal Growth of the Single-Comb White Leghorn 375 
In single-comb White Leghorns the 
wing feathers begin to appear very 
early and the rest of the plumage is 
developed earlier than in some other 
breeds. The weight of the feathers 
increases more rapidly than the body 
weight, increasing from a little over 
4.5 per cent to nearly 8 per cent of 
the net body weight, and then de¬ 
creasing again. 
After 1,260 gm. gross body weight 
there is a sex difference in the per¬ 
centage weights. The absolute weight 
of the feathers increases without any 
sex difference until the body weight 
reaches 1,270 gm.; then the curve for 
the females begins to decline. The 
the structure of the feathers. Until 
the feather is completely developed, 
the shaft contains a large amount of 
vascular tissue, but later the vascular 
tissue in the shaft atrophies and dries 
out. This results in a marked decrease 
in weight of the plumage. The female 
plumage is completed before that of 
the male, thus resembling the growth 
of the body as a whole and the ossi¬ 
fication of the skeleton, as already 
shown. 
Weiske (SO) reports an increase fol¬ 
lowed by a decrease in the absolute 
and relative weights of the feathers in 
his 12 specimens. In the newly hatched 
chick weighing 40.9 gm. the weight of 
Fig. 10 .—Individual weights of the combs and the two wattles (combined), plotted on gross body 
weight. Ear lobes are shown for the older chickens only. The encircled dots represent the ear lobes 
of the male; the double circles, weight of the ear lobes of the females. No curve was drawn for this 
chart since the data are too irregular 
curve for the male plumage increases 
up to a gross body weight of 1,640 gm. 
and then it too decreases. The sex 
plumage, the sickle feathers, saddle 
.feathers and the long feathers on the 
neck are the last to develop, and the 
growth of these probably carries the 
curve for the male plumage to a higher 
level than that reached by the female 
plumage. The same rise, followed by 
a decrease in the female and later in 
the male plumage, is also observed 
when the absolute weights are plotted 
against age. 
This rise and fall in both relative 
and absolute weights, plotted against 
both the gross body weight and against 
time, are correlated with changes in 
the feathers is given as 0.7295 gm. 
The maximum weight given is 83.59 
gm. at 34 weeks when the gross body 
weight is 1,094 gm. From this point 
the weight of the feathers decreases to 
57.23 gm. at one year. 
The percentage values rise from 3.07 
per cent at hatching to a maximum of 
14.61 per cent at 660 gm. gross body 
weight (twenty-fourth week) and again 
decrease to 6.86 per cent at one year 
of age or a gross body weight of 1,360 
gm. 
Comb and wattles. —Figure 10 
shows the absolute weights of the 
comb and wattles combined, and the 
weights of the two ear lobes (com¬ 
bined) for the older chickens. All are 
