STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 49 
network. The principal difference between the comb of 
a cock and of a hen lies in the fact that the former consists 
principally of tough fibrous connective tissue and is highly 
vascular, and this is the reason of the erect carriage and 
bright red colour of the cock’s comb. The hen’s comb, on 
the other hand, is not quite so vascular, and has the central 
core loaded with infiltrated fat, especially at the breeding 
periods. Hence it has a. tendency to droop over when it 
becomes large and heavy, as the fibrous walls are not power- 
ful enough to support the weight of the fat. 
The cock’s comb does not exhibit the striking and rapid 
periodic fluctuations in size characteristic of the hen’s comb 
at the breeding times. At a very early age the cock’s comb 
begins to increase steadily and slowly, so as to outstrip that 
of the young hen of the same age and breed, but after it has 
attained its full size it does not undergo any marked altera- 
tions in size unless as the result of ill-health. We have 
shown that the fluctuations in the hen’s comb are due to 
rapid deposition or abstraction of fat from the comb, and 
since this fat is practically absent from the cock’s comb it is 
easily intelligible why the cock’s comb does not undergo any 
rapid alterations in size. 
The conclusions to be drawn from this study of the hen’s 
comb are of considerable importance for our attempt at 
analysing the changes occurring in the animal body at 
periods of reproductive activity. At the time when the 
female bird is forming the large-yolked eggs, and is presum- 
ably tranferring large quantities of fatty material to the 
ovary, we observe a change in one of its bodily organs — the 
comb — due to a deposition of fatty material in it. The blood 
at this time is probably charged with an excess of fat or 
yolk-forming material, and this excess which is not taken up 
by the ovary is deposited in the subcutaneous tissue of the 
comb, and probably in other situations as well. A correla- 
tion is therefore established between the comb and the ovary, 
which is due, not apparently to any specific internal secretion 
or hormone elaborated by the ovary, but to the blood becoming 
