Large injections of progesterone have been shown to 
completely and immediately stop egg production followed in 10 to 
14 days by a rapid moit (Herrick et al., 1955). The molt ceased 
2 weeks after final injection and egg production resumed in 25 + 
2.6 days after final injection according to Adams (1955). Cook” 
and Warnick (7961) classified a group of pullets into four pro- 
duction levels on the basis of past production. They then gave 
these birds various levels of progesterone for two weeks and 
observed them for twenty weeks after treatment. The injections 
were given every third day at the following levels. The pro- 
duction levels during the two weeks of treatment and after treate- 
ment for four weeks are listed. 
Treatment: 0 2 4 8 16 32 £64me. 
Treatment production: 10.2 10.5 669 4.2 2.1 ®,9 2.4Ege6 
4eweek post treat. prod.: 18.2 19.4 15.0 15.9 9.5 9.0 -JEggs 
After the four-week post-treatment period, production was the 
same in all groups. There was a linear response of production 
groups over all levels of progesterone, with high production 
groups showing less inhibition. This would suggest a possible 
genetic difference in resistance to gonadotropic inhibition. 
The physiological basis for progesterone hormonal de- 
pression on egg production is presumably through its influence 
on the pituitary as a depressor of gonadotropic hormone secretion 
rate. Herrick and Adams (1955) showed that progesterone had the 
least lasting effect, followed by testosterone and lastly 
diethystilbestrol. 
One other group of estrogen treatment studies should 
be mentioned here. This work segms to have a definite effect on 
sex ratio, although the physiological basis is not clear. Fraps 
and co-workers in 1956 injected 9=-week old pullets with either 
1, 2, 4, or 8 pellets of 15 mg. of diethylstilbestrol. The 
numbers of chicks that developed from eggs from these treated 
hens were found to be definitely heavy on the female side during 
the fourth and fifth months of production, but not after that. 
In a hatch of more than 30 chicks, the ratio was 40 per cent 
males and 60 per cent females. In another hatch of 67 chicks, 
the ratio was 42 per cent males and 58 per cent females. In 
1958, Pun did a similar experiment with 34 Brown Leghorn hens 
using 30 me. stilbestrol tablets. His results were similar to 
Fraps -~ of 590 chicks from treated females, 57.6 per cent were 
females whereas in 252 chicks from controls, only 46.8 per cent 
were females. He noticed the same period of greatest effect and 
then a return to a normal ratio. Pun suggested that his and 
Frap's results were due either to selective elimination of the 
male chromosomal complement as a polar body or to sex reversal 
of genetic males to females by the treatment. He tried to test 
the latter hypothesis with 54 females of which three should 
have been sex reversed. These three should produce all males. 
56 
