THE GONADOTROPIC HORMONES 



mals.^^ Saunders and Cole (1936) showed that only the ovar- 

 ian interstitial tissue is stimulated in rats 10-15 days old, 

 whereas follicular stimulation was marked in animals 18 days 



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 A fioiiU 6/- //Jtoci 

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Fig. 19. — The rate of disappearance of the gonadotropic hormone of pregnant- 

 mare serum following the intravenous injection of 3,000 rat-units into rabbits. 

 (From Catchpole, Cole, and Pearson, Amer. J. Physiol., 112, 21-26 [1935].) 



old, and ovulation and corpus luteum formation appeared 

 with increasing frequency in still older rats (19-25 days old.)^^ 



^^ Wells (1937) describes the action of the hormone in a hermaphrodite ground 

 squirrel. 



Engel (1936) and Engel and Buno {1936) believed that certain pineal extracts 

 antagonize the gonadotropic action of the hormone. 



^' None of the rats was hypophysectomized. However, others, including Ham- 

 burger, have observed the formation of lutein tissue in hypophysectomized rats re- 

 ceiving an extract of pregnant-mare serum. 



[147] 



