MAMMARY GLAND AND LACTATION 



593 



PwokcTiL del 



Fig. 101. Sex difference in the development of tlie mammaiy bud of the fetal mouse and 

 effect of androgen on the histogenesis of the female mammary bud. A. First inguinal gland 

 of female fetus (15 days, 17 hours). B. First inguinal gland of male fetus (15 days, 17 hours). 

 C. Second inguinal gland of female fetus (15 days, 16 hours) from a mother receiving testos- 

 terone propionate. D. First inguinal gland of female fetus from the same litter as that in C. 

 (From A. Ravnaud, Ann. endocrinol., 8, 248-253, 1947.) 



For further information on the morpho- 

 genesis of the mammary ghmd, the reader 

 is referred to the recent detailed accounts 

 by Dabelow (1957) and Raynaud (1960). 



B. NORM.\L POSTNATAL DEVELOPMENT 



1. Methods of Assessing Mammary Devel- 

 opment 



In the last two decades the increasing 

 availability of the ovarian hormones in pure 

 form and the prospect of the large scale 

 practical application of fundamental knowl- 

 edge of the hormonal control of the mam- 

 mary gland to the artificial stimulation of 

 udder growth and lactation in the cow, have 

 together effected a demand for greater ac- 

 curacy in studying and assessing the degree 

 of mammary development. Various quanti- 

 tative and objective procedures have now 

 been evolved which allow results of develop- 

 mental studies to be subjected to statistical 

 investigation. These methods have been re- 



viewed recently (Folley, 1956) and we need 

 but mention them briefly. 



In those species in which, save in late 

 pregnancy, the mammae are more or less 

 flat sheets of tissue, the classical whole- 

 mount preparations have been the basis for 

 several quantitative studies. From such 

 preparations the area covered by the duct 

 systems can be measured by suitable means 

 (e.g., as in our studies on the rat mammary 

 gland; Cowie and Folley, 1947d), thus pro- 

 viding an accurate measure of duct exten- 

 sion. Such measurements, however, give no 

 information on the morphologic changes 

 within this area and so a semiquantitative 

 scoring system to assess the degree of duct 

 complexity has been used in conjunction 

 with the measurements of area (see Cowie 

 and Folley, 1947d) . More reliable and objec- 

 tive techniciues for measuring duct complex- 

 ity were later developed in our laboratory by 

 Silver (1953a) and Flux (1954a). Species 

 such as the guinea pig in which the gland, 



