TRANSPLANTATION INTO MAMMARY FAT PADS 



567 



of problems. In the following paragraphs the nature of some of our recent studies, 

 both published and unpublished, complete and incomplete, is indicated. 



The nature of the interaction of tissues cotransplanted into the same fat pad can be 

 determined. The transplantation of one or more pieces of mammary tissue into one 

 fat pad has revealed the presence of a growth-regulating system in the mammary gland 

 which determines both the extent of growth and the spacing of ductal elements. 347 



Fig. 94. Drawing of a right no. -4 fat pad from a three-week-old female mouse. 



The blood vessels, fat pad, and nipple area were cauterized along the slant lines. The 

 fat pad and the surrounding connective tissue bounded by the broken line were removed 

 with fine scissors. 225 A. Boundary of no. -4 fat pad; B. Large vein; C. Inguinal lymph 

 node; D. Portion of no.-5 fat pad; E. Branching ducts of the no. -4 mammary gland; 

 F. Nipple area. 



Figs. 95 and 96. Right no. -4 pad of a 15-week-old, virgin, C3H/Crgl female mouse. 



Left. The normal gland has developed from a mammary lobule (taken from a pregnant, 

 C3H/Crgl, female mouse) which was transplanted into the pad when the host was three 

 weeks of age. 4X. 



Right. The hyperactive outgrowth has developed from an hyperplastic alveolar nodule 

 (taken from a tumor-bearing, nonpregnant, nonlactating, multiparous, adult, C3H/Crgl 

 female mouse) which was transplanted into the pad when the host was three weeks of age. 4X. 



