STUDIES TN THE EXPERIMENTAL ANALYSIS OF SEX. 47 
do with the comb-increase, the whole phenomenon being con- 
trolled by the periods of egg-laying. 
A record was also kept of the weight in grammes of the 
birds under observation, but it was found that the sudden 
increase of the comb was not accompanied by an increase in 
general body-weight. An increase in body-weight generally 
comes some time before the comb shows its rapid growth, but 
while the comb-growth is proceeding the body -weight 
remains stationary or may even sink. 
Having established the close correlation between comb- 
increase and egg-laying, an inquiry was made into the 
processes occurring in the comb duriug the remarkably rapid 
growth periods. If sections are made through the comb of 
a hen which has recently exhibited a rapid increase, it will 
be found that the central core of the comb consists of a mass 
of solid fat, which has completely infiltrated the loose connec- 
tive tissue usually present in this situation (Text-figs. 1 and 4). 
Immediately underneath the external epithelium of the comb 
numerous blood-capillaries are seen cut across, and the walls 
of the comb are found to consist of fibrous connective tissue. 
If, now, we take similar sections through the comb of a hen 
which has recently been decreasing in area (Text- fig. 2), we 
shall find that the central core is smaller and no longer con- 
tains a solid mass of infiltrated fat, but only comparatively 
few and small fat-globules. The connective-tissue walls of 
the comb, on the other hand, are not found to have conspicu- 
ously diminished in size. The blood-capillaries under the 
epithelium are fewer in number and more reduced. It is 
clear, then, that the chief cause of the increase in size of the 
comb is a fatty infiltration of its central core, and to a much 
less extent a. greater blood supply. Let us now compare the 
condition in a normal cock bird (Text-figs. 3 and 5). Here it 
is seen that the central connective-tissue core (c.) is small 
relatively to the fibrous connective-tissue walls (/.) of the 
comb, and that it contains a very few small globules of fat 
compared to the comb of a female bird. The blood capillaries 
[y.\ lying under the epithelium (eji.) form a richly vascular 
