452 



MANUAL OF HISTOLOGY. 



DEVELOPMENT OF THE GLAND. 



Like the other cutaneous glands of the body, the mamma 

 is first formed by a proliferation inward of certain epidermal 

 cells. In other words, the breast results from a downward 

 extension of epiblastic corpuscles. The first unmistakable indi- 

 cation of the future gland is seen about the third or fourth month 

 of pregnancy. At that time it consists of a solid plug, or pro- 



Fio. 196. 1. Rudimentary form of gland 

 in human fcetus: a, 6, epidermis : c, aggrega- 

 tion of cells ; d, connective tissue layer. 2. From 

 a seven-months' foetus : a, central substance ; 

 &, larger, and c, smaller outgrowths. Frey. 



FIG. 197. Embryonal mamma : a, cen- 

 tral mass, with 6, and c, variously shaped 

 outgrowths. Frey. 



cess, extending downward from the rete-mucosum of the skin. 

 This has been called Drusenfeld, by Huss. From the internal 

 end of this solid process, sprouts, or offshoots, are developed, 

 and they represent the future separate glands constituting the 

 mature organ. These buds have a pyrif orm, or club-like shape, 

 and are surrounded by ordinary embryonal connective tissue. 

 The further growth of the gland takes place by a process of 

 continuous extension and subdivision, but indications of the 

 latter are not always found at birth. Ducts are already visible 

 in the new-born infant, but the aggregations of cells represent- 

 ing the future acini, remain without lumina for a much longer 

 period. 



Th. Kolliker describes as a constant occurrence, especially 

 marked in the breasts of female infants, the dilatation of a 

 greater or smaller number of milk-ducts. Such ectatic-canals 



