THE LACTOGENIC HORMONE 



velopment of the breasts is not observed in the spayed female 

 of the experiment ? 9p (Ernst, 1927; Zacherl, 1928; and 

 Hill, 1932). Zacherl cites the cases of the pygopagous sisters, 

 Blacek, one of whom became pregnant; after parturition, 

 lactation also occurred in the non-pregnant twin. 



Kallas (1929) produced parabiosis between rats weighing 

 50-100 g. according to the schemata cT ? and gTisT- He then 

 transplanted ovarian tissue into the normal male in which the 

 breasts subsequently developed, forming alveoli but not 

 lactating. In three pairs of rats, living in parabiosis accord- 

 ing to the plan cf 9 p. Hill (1932) found that there was little 

 development of the breasts in the female and no lactation 

 after parturition. 



Other experiments in which lactation has been produced by 

 the injection of anterior-lobe extracts into mammals ^^ — The ex- 

 tent to which anterior-lobe extracts can cause development 

 of the breasts is still a debated question. It appears that 

 growth of the breasts, roughly comparable to that of puberty, 

 must have occurred before an anterior pituitary extract will 

 cause either further growth or lactation. In the rabbit and 

 mouse, an anterior-lobe extract may cause a further develop- 

 ment of the breasts after ovariectomy.'' In the female rat, 

 breast development seems to depend almost entirely upon 

 the internal secretions of the ovary; the breasts rapidly 

 undergo involution in ovariectomized pregnant rats despite 

 the administration of homo-implants or anterior-lobe extract 

 (Evans and Simpson, 1931). 



The injection of extracts of the pars glandularis has pro- 

 duced or altered lactation in the following animals: guinea 

 pig (6, 17, 18); rabbit (i, 2, 3, 7, 14, 15); dog (i, 2, 12, 16); 



''Riddle, Lahr, and Bates (1935) concluded that the lactogenic hormone may 

 cause maternal behavior in rats (virgin rats 67-81 days old which had first received 

 injections of prolan or anterior-pituitary gonadotropic hormone). 



'" Corner (1930), Bradbury (1932); and Lyons and Catchpole (1933). 

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