10 



THE MAMMARY GLAND 

 AND LACTATION 



A. T. Cowie and S. J. FoUeij 



NATIONAL INSTITUTE FOR RESEARCH IN DAIRYING, SHINFIELD, 

 READING, ENGLAND 



I. Introduction 



I. Introduction 590 



II. Development of the Mammary 



Gland 591 



A. Histogenesis 591 



B. Normal Postnatal Development . 593 



1. Methods of assessing mammary 



development 593 



2. Mammary development in the 



nonpregnant female 594 



3. Mammary growth in the male . . 595 



4. Mammary development during 



pregnancy 596 



5. Mammary involution 598 



C. Experimental Analysis of Hormonal 



Influences 598 



1. Ovarian hormones in the animal 



with intact pituitary 598 



2. Anterior pituitary hormones. . . 601 



3. Metabolic hormones (corticoids, 



insulin, and thyroid hormones) 604 

 III. Endocrine Influences in Milk Se- 

 cretion 606 



A. Anterior Pituitary Hormones 606 



1. Initiation of secretion (laeto- 



genesis) 606 



2. Maintenance of milk secretion — 



galactopoiesis 609 



3. Suckling stimulus and the main- 



tenance of lactation 611 



B. Hormones of the Adrenal Corte.x . . 612 



C. Ovarian Hormones 613 



D. Thyroid Hormones 617 



E. Parathyroid Hormone 618 



F. Insulin 619 



IV. Removal of Milk from the Mammary 



Glands: Physiology of Suckling 

 AND Milking 619 



A. Milk-Ejection Reflex 619 



B. Role of the Neurohypophysis 621 



C. Milk-Ejection Hormone 622 



D. Effector Contractile Mechanism of 



the Mammary Gland 623 



E. Inhibition of Milk Ejection 624 



F. Neural Pathways of the Milk-Ejec- 



tion Reflex 625 



G. Mechanism of Suckling 626 



V. Relation between the Reflexes 



Concerned in the Maintenance of 

 Milk Secretion and Milk Ejection 627 

 VI. Pharmacologic Blockade of the Re- 

 flexes Concerned in the Main- 

 tenance OF Milk Secretion and 



Milk E.tection 630 



VII. Conclusion 632 



VIII. References 632 



This account of the hormonal control of 

 the mammary gland is in no way intended 

 as an exhaustive treatment of mammary 

 gland physiology, but rather an attempted 

 synthesis of current knowledge which it is 

 hoped will be of interest as an exposition of 

 the authors' conception of the present status 

 of the subject. Since the publication of the 

 second edition of this book, the emphasis 

 in the field under review has tended to shift 

 towards the development of quantitative 

 techniques for assessing the degree of mam- 

 mary development, towards attempts at a 

 ])enetration into the interactions of hor- 

 mones with the biochemical mechanisms of 

 the mammary epithelial cells, and towards 

 an increasing preoccupation with the in- 

 terplay of nervous and endocrine influences 

 in certain phases of lactation. The reader's 

 acquaintance with the classical foundations 

 of the subject as described in the second 

 edition of this book (Turner, 1939) and in 

 other subsequent reviews (Follcy, 1940; 

 Petersen, 1944, 1948; Folley and Malpress, 

 1948a, b; Mayer and Klein. 1948, 1949; 

 Follev, 1952a, ]9r)6; Dabelow. 1957) will 



590 



