THE LACTOGENIC HORMONE 



growth of the breasts has been stimulated solely by the ad- 

 ministration of oestrone (experiments in males by Nelson, 

 1935). Lactation occurs in the male rat several days after a 

 long course of oestrin treatment has been discontinued (Hal- 

 pern and D'Amour, 1934). 



It therefore appears that the development of the breasts 

 due to "oestrin" alone is preparation sufficient to permit the 

 lactogenic hormone to cause lactation in three different 

 animals: the rabbit, the guinea pig, and the rat. According 

 to Bradbury (1932), this is not the case in the mouse. 

 Oestrone and oestriol ("Theelin" and "Theelol") caused de- 

 velopment only of the galactophores. The development of 

 the secondary ducts and the alveoli seemed to require the 

 secretion of the corpus luteum hormone as well as (a secretion 

 of?) the uterus. If hysterectomy was performed before lutein- 

 ization of the ovaries was produced (anterior-lobe extract or 

 prolan), the secondary ducts did not develop. However, an 

 extract of the sheep pituitary (but not prolan) caused a de- 

 velopment of the alveoli even after ovariectomy and hyster- 

 ectomy, provided that some growth of the secondary ducts 

 was already present. 



2. The uterus. — A puzzling but perhaps important factor 

 in the physiology of the lactogenic hormone is the uterus.'^ 

 Bradbury (1932) reported that lactation followed hyster- 

 ectomy in the mouse after anterior-lobe extract had been in- 

 jected to bring about a development of the mammary-gland 

 alveoli. In pregnant mice (eleventh day of gestation), hyster- 

 ectomy was followed by lactation, De Jongh (1934) ad- 

 ministered 50 rat-units of oestrone daily to female rats. After 

 2 weeks the treatment was stopped; lactation then usually 

 appeared if the uterus was removed also. According to Selye, 

 Collip, and Thomson (1934), cesarean section late in preg- 

 nancy (rat) is followed by lactation; lactation is prevented, 



" Usually the authors do not indicate whether or not experimental hysterectomy 

 may have interfered with the ovarian circulation. 



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