384 
Journal of Agricultural Research 
Yol. XXIX, No. S 
RESPIRATORY SYSTEM (TRACHEA AND 
lungs) 
The lungs and trachea were removed 
and weighed together. Their growth 
in gross and relative weight is shown in 
Figure 19. The formula is: 
Y — (0.01X + 1) 1 * 1 —0.0056X —0.88 
from 30-1,200 gm. gross body weight. 
Y represents the weight of the liver 
in grams and X the gross body weight, 
also in grams. Up to 1,200 gm. in 
gross body weight, the cases fall fairly 
well in line; but above this weight there 
is a great deal of variation and conse¬ 
quently the mathematical curve is car¬ 
ried only this far. The same condi¬ 
tion is seen when the weights are 
sex difference is also shown in the curve 
of the relative growth. The relative 
weights of the two sexes are shown by 
separate curves from 1,200-2,200 gm. 
gross body weight. There is a great 
deal of variation in the percentage 
values, and the curves shown in Figure 
19 are merely the inspection curves 
drawn through the double-weighted 
medians. The relative weights for the 
individual chickens are not shown. 
Donaldson ( 3 ) shows no sex difference 
for the lungs in the rat, and no sex 
difference is found in the human species. 
It hardly seems probable that the crow¬ 
ing of the cockerel would make this 
difference, but this seems to be the 
only explanation for the apparent sex. 
difference. 
Fig. 20.—Growth of the heart ploted on gross body weight. The heavy line shows absolute weight. The 
lightert line shows relative or percentage weights 
plotted on age. The cases are regu¬ 
larly arranged up to about 120 days, 
after which they are more irregular, 
especially in the males. When the 
blood was allowed to drain from the 
body as previously described a marked 
difference in the amount was noticed. 
In some specimens the blood coagu¬ 
lated much sooner and thus a larger 
amount remained in the chicken. 
Thompson and Carr {26) find a marked 
variation in the time of coagulation of 
the blood in the domestic fowl (Ply¬ 
mouth Rocks). The lungs are very 
vascular and this difference in the 
amount of blood may account for some 
of the variability of the lungs as well as 
some of the other vascular organs. 
There is apparently a sex difference 
in the respiratory tract in the chickens 
above 1,200 gm. in body weight. This 
CIRCULATORY SYSTEM (HEART) 
The weights of the heart in grams 
and the percentage weight plotted 
against the gross body weight are 
shown in Figure 20. The formulas are: 
F=X 0 - 2 4*0.0027X —2.08 
from 50-1,400 gm. gross body weight,. 
F=0.007(X-1,400) +5.96 
from 1,400-2,500 gm. gross body 
weight. 
F represents the weight of the heart 
in grams and X the gross body weight 
in grams. 
Here also as in the case of the lungs, 
there is an apparent tendency to a sex- 
difference toward the end of the curve.. 
