DEVELOPMENT OF THE MAMMARY GLANDS. 



283 



further observed certain kinds of fine fibres which it was 

 impossible to follow further, and which appear to terminate 

 at the outer surface of the hyaline layer, but I was unable 

 to ascertain whether these were nerve fibrils or not. 



Fig. 208. 



Fig. 208. Terminal dilatations of the ducts of the mamma in a Girl 

 fourteen years of age. System 4, Hartnack. 



From all this then it would appear that the process of 

 formation of the glandular elements may be correctly regarded 

 as a continuously progressive budding, and it is scarcely 

 possible to doubt that it is immediately dependent on a proli- 

 feration of the epithelial cells ; it is also certain that in pro- 

 portion as the system of ducts proceeds to form acini, the 

 intervening dense stroma becomes gradually looser in texture 

 and diminished in quantity, though the causative relations of 

 these two processes may be scarcely capable of histological 

 definition. It is yet worthy of observation that, coincidently 

 with the formation of the acini, fat cells make their appearance 

 in the stroma, which are unquestionably to be regarded as a 

 secondary product of these processes. 



