THE PITUITARY BODY 



The experiments discussed in the preceding paragraph sug- 

 gest that either corpus luteum hormone or oestrin may an- 

 tagonize the lactogenic effect of anterior-pituitary secretion. 

 Several investigators have reported that the injection of 

 "oestrin" or oestrone inhibits lactation (mouse, rat, and 

 guinea pig).^ How this effect is produced is not clear; it seems 

 likely that oestrin interferes both with the secretion of the 

 lactogenic hormone and with the effect of this hormone on 

 the mammary gland.^ If, after the repeated administration 

 of oestrone to guinea pigs or rats, the dose is reduced or no 

 more oestrone is given, lactation is frequently observed 

 within a few days (De Jongh and Laqueur, 1930; De Jongh, 

 1934). De Jongh concluded that hysterectomy after the 

 period of oestrone-treatment facilitated the appearance of 

 lactation in rats at least. 



What ovarian secretion (or secretions) prepares the mam- 

 mary gland so that the lactogenic hormone can act? In the 

 rabbit it appears that only the development due to "oestrin" 

 secretion is necessary. Evidence supplementing the observa- 

 tions of Corner and others was furnished by Frazier and Mu 

 (i935)> who observed, in male rabbits, lactation which ap- 

 peared after injections of oestrin" had been given about 3 

 months. Injections of oestrin were then continued; lactation 

 was present for 90-200 days. (Such findings are clearly not 

 similar to those of others in mice, rats, and guinea pigs in 

 which oestrin has been observed to interfere with lactation.)" 

 In the guinea pig, also, the mammary gland will secrete milk 

 in response to the lactogenic hormone provided that the 



* De Jongh (19J3); Nelson (1934-35); and others. 



' Nelson (1935) reported that the administration of a sufficiently large dose of 

 oestrone prevented lactation which otherwise followed the administration of an 

 anterior-lobe extract. Also see the discussion, below, of the experiments of Frazier 

 and Mu. 



'" A butyl-alcohol extract of pregnancy-urine. 



" Kunde, D'Amour, Carlson, and Gustavson (1930) injected oestrin repeatedly 

 into dogs. In one female dog lactation appeared and persisted (with suckling) 

 throughout the period of injection. 



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