DEVELOPMENT OF THE GLAND. 453 



liave their lumina filled with desquamated epithelial cells, and 

 a whitish, granular material. Formerly, these occurrences were 

 considered to be exceptional, and were regarded as having a 

 pathological significance. During the first year of extra-uterine 

 life, this characteristic process of progressive dilatation may 

 assume such large dimensions, that the mamma may come to 

 resemble cavernous tissue, the ectatic spaces of which are 

 paved with flattened epithelium. Within certain limits, Kolli- 

 ker regards this as a perfectly normal physiological event. But 

 he adds that an exaggerated process of this kind may result in 

 early mastitis. Such an occurrence, he thinks, may explain 

 the rudimentary development of the breasts observed in some 

 women of otherwise normal growth. 



The post-embryonal growth of the mamma has been care- 

 fully studied by Langer, and his results and conclusions having 

 been confirmed by the investiga- 

 tions of Kolliker, Huss, and others, 

 must still be received as represent- 

 ing the true condition of things, in 

 spite of the novel and heterodox 

 views advanced by Creighton. 



Up to the time of puberty, the 

 growth of the breast is very grad- 

 ual and quite insignificant, even in 

 females. Then, however, the ducts 

 begin to rapidly ramify in all di- 

 rections, and, by offshoots from va- 

 rious points, true acini are at length 

 developed. But they remain of 

 small size until the stimulus of 

 pregnancy causes a further evolution. In the male, the exist- 

 ing ducts, as a rule, atrophy with advancing age. The evolu- 

 tion changes which the mamma undergoes during pregnancy, 

 have already been set forth, and there remain to be considered 

 only those final phases of metamorphosis which take place in 

 the climacteric period of life. 



These are readily understood, consisting essentially of a 

 complete atrophy of all the secreting acini. Simultaneously 

 with these atrophic changes the epithelia of the galactophorous 

 ducts become flattened, and finally shrink, so as to form only 

 squamous plates, which line the ramifying processes of connec- 



