GESTATION 



969 



± 5 - 



3 - 



24 



28 



4 8 12 16 20 



TIME IN DAYS 

 Fig. 16.7. Concentration of gestagen in the blood of the normal pregnant rabbit as de- 

 termined by the Hooker-Forbes test. (From M. X. Zarrow and G. M. Neher, Endocrinology, 

 56, 1, 1955.) 



12 16 



TIME IN DAYS 



20 



Fig. 

 tion in 

 Zarrow 



16.8. The effect of castration on serum progestogen levels and maintenance of gesta- 

 the rabbit. Gestagen levels were determined by the Hooker-Forbes test. (From M. X. 

 and G. M. Xeher. Endocrinology, 56, 1, 1955.) 



changes in serum gestagen levels before 

 and after castration of a pregnant rabbit. 

 The concentration increased from a level of 

 0.3 ing. per ml. at day to 10 /xg. per ml. on 

 day 24 when the rabbit was castrated. A 

 60 per cent drop in serum gestagen level is 

 seen 12 hours after castration with a fur- 



ther drop at the 36th hour, when the animal 

 aborted. 



Studies on the concentration of serum 

 gestagen in the pregnant ewe (Neher and 

 Zarrow, 1954) permit a comparison with 

 the results obtained in the rabbit. Such a 

 comparison is extremely valuable in view 



