374 
Joumal of Agricultural Research 
Vol. XXIX, No. 8 
comb, and wattles, plotted on gross 
body weight, also its percentage of 
the net body weight. The formula 
is: 
F=0.0836X 
in which Y represents the weight of 
the integument in grams and X the 
gross body weight in grams. 
From this chart it is clearly evident 
that the growth of the skin is in direct 
proportion to the total increase in 
body weight, and that there is no 
appreciable sex difference. The per¬ 
centage weights of the skin show no 
marked changes, forming about 8.9 
per cent of the net body weight. 
not left in the skin to be weighed 
with the integument. 
Feathers. —The growth of the 
feathers (fig. 9) follows a course en¬ 
tirely different from that of any of 
the preceding curves. To some extent 
it resembles the growth of the thymus 
(fig. 22). 
The formulas for the males are: 
Y = (0.01X) l,4 + 0.0545X—0.45 
from 100-600 gm. gross body weight, 
r=o.i (;;-6oo)+ 44.53 
from 600-1,640 gm. gross body weight, 
Y= 148.53 — 0.04 (X- 1,640) 
Fig. 9—Weight in grams and percentage weight of the feathers. The abscissa represents the gross body 
weight. The case at 1,210 gm. and all of those above 2,200 gm. gross body weight are shown on the 
chart though not included in the data for the formula. A sex difference is apparent in the larger 
specimens 
This is less than the figures given by 
Welcker and Brandt {28), who give 
18.86 per cent for the skin and sub- 
dermal fat for the domestic fowl, and 
from 12.57 to 18.07 per cent for the 
skin only of the other species of birds 
investigated. Their percentage weights 
doubtless include the feathers, how¬ 
ever, which would make them more 
nearly comparable with those in the 
charts. The percentage weights of 
the skin for the various animals as 
given by Welcker and Brandt show a 
wide range and are in most cases 
greater than the values found in the 
Minnesota chickens (without feathers). 
According to Wiedersheim {29), the skin 
of birds is relatively thin; moreover, 
in removing the feathers, the shaft is 
from 1,640-2,400 gm. gross body 
weight. 
The formulas for the females are: 
Y= (0.01X) 1 ' 4 + 0.0545 A^ — 0.45 
from 100-600 gm. gross body weight, 
F = 0.1 (X-600)+44.53 
from 600-1,270 gm. gross body weight, 
K=lll.53-0.038 {X— 1,270) 
from 1,270-1,900 gm. gross body 
weight. 
In all these formulas Y represents 
the weight of the feathers in grams 
and X represents the gross body weight 
in grams. 
