MAMMARY GLAND AND LACTATION 



601 



Fig. 10.5. Wliole mounts of breast of an ovariectomized immature female rhesus monkey 

 before (left) and after (right) e.strogen treatment. (From H. Speert, Contr. Embrvol., 

 Carnegie Inst. Washington, 32, 9-65, 1948.) 



the necessary experiments be done the 

 human breast would show a considerable 

 growth response to estrogen alone. 



Finally, in the third category are those 

 species in which estrogen in physiologic 

 doses causes little or no mammary growth. 

 The bitch and probably the ferret seem to 

 belong to this class (see Folley, 1956). 



There has been considerable discussion 

 in the past regarding the ratio of proges- 

 terone to estrogen optimal for mammary 

 growth. Only recently, however, has this 

 question been fully investigated in any spe- 

 cies. Benson, Cowie, Cox and Goldzveig 

 (1957) have shown that in the guinea pig 

 the absolute quantities of progesterone and 

 estrogen are the crucial factors in controlling 

 mammary growth; altering the dose levels 

 but maintaining the ratio gave entirely dif- 

 ferent growth responses. In view of the 

 varying ability of the different estrogens to 

 stimulate mammary duct growth (Reece, 

 1950) it is essential in discussing ratios to 

 take into consideration the nature of the 

 estrogen used, a fact not always recognized 

 in the past. 



2. Anterior Pituitary Hormones 



Soon after the discovery by Strieker and 

 Grueter (1928, 1929) of the lactogenic ef- 

 fects of anterior iiituitarv extracts, it was 



shown that anterior i)ituitary extracts had a 

 mammogenic effect in the ovariectomized 

 animal and that the ovarian steroids had 

 little or no mammogenic effect in hypophy- 

 sectomized animals. C. W. Turner and his 

 colleagues postulated that mammogenic ac- 

 tivity of the anterior pituitary was due to 

 specific factors which they termed "mam- 

 mogens"; other workers, in particular 

 W. R. Lyons, believed the mammogenic ef- 

 fect was due to prolactin. The theory of spe- 

 cific mammogens has been fully reviewed in 

 the past (Trentin and Turner, 1948; Folley 

 and Malpress, 1948a) and we do not propose 

 to discuss it further for there is now little 

 evidence to support it. Damm and Turner 

 ( 1958) , while recently seeking new evidence 

 for the existence of a specific pituitary mam- 

 mogen, concur in the view expressed by 

 Folley and Malpress (1948a) that final 

 proof of the existence of a specific mam- 

 mogen will depend on the development of 

 l)etter assay techniques and the characteri- 

 zation or isolation of the active principle. 



The mammogenic effects of prolactin were 

 observed in the rabbit by Lyons (1942) 

 who injected small quantities of prolactin 

 directly into the galactophores of the suit- 

 ably prepared mammary gland. IV'Iilk secre- 

 tion occurred but Lyons also noted that the 

 l)rolactin caused active growth of the alveo- 



