CHAPTER V 



THE PARS GLANDULARIS OF THE PITUITARY 

 BODY IN RELATION TO THE DEVELOPMENT 

 OF THE BREASTS AND THE SECRE- 

 TION OF MILK^ 



THE relationship between lactation and the secretory 

 activity of the pars glandularis is complex and only 

 incompletely understood.'' It is agreed that the lacto- 

 genic hormone initiates and maintains lactation. However, 

 its presence in adequate concentration in the blood is a neces- 

 sary but not a sufficient condition of lactation. Moreover, 

 preceding lactation there must be proper development of the 

 mammary glands. The extent to which this prelactation 

 growth depends either directly on an internal secretion of the 

 pars glandularis or indirectly on gonadotropic hormones 

 which increase gonadal function is still a problem undergoing 

 active investigation. 



Lactation cannot continue in the absence of the pituitary 

 body. The correctness of this statement which has been gen- 

 erally held for some years was recently again confirmed in the 

 guinea pig (Gomez and Turner, 1936; Macchiarulo, 1936) and 

 in the dog (Houssay, 1935). The other aspect of this dis- 

 covery is represented by the following question: After hy- 

 pophysectomy in a lactating animal, can lactation be main- 

 tained by the lactogenic hormone alone, or are several an- 

 terior pituitary hormones required? In the pigeon, according 

 to Schooley, Riddle, and Bates (1937), proliferation of the 

 crop-glands and the formation of crop-milk, which are 

 changes homologous to breast development and lactation in 



' The pars neuralis, pars intermedia, and pars tuberalis have not been shown to 

 be of significance. '*• 



' See also reviews of other work in chaps, iii and iv. 



