78 SECRETION. 



tached to the pectoralis major. A considerable amount 

 of adipose tissue is also found in the substance of the gland, 

 between the lobes. 



Separated from the adipose and fibrous tissue, the organ, 

 is found divided into lobes, from fifteen to twenty-four in 

 number. These, in their turn, are subdivided into lobules 

 made up of a greater or less number of acini or culs-de-sac. 

 The secreting structure is of a reddish-yellow color, and is 

 distinctly granular, presenting a decided contrast to the pale 

 and uniformly fibrous appearance of the gland during the 

 intervals of lactation. If the ducts be injected from the 

 nipple and be followed into the substance of the gland, each 

 one will be found distributing its branches to a distinct 

 lobe ; so that the organ is really made up of a number of 

 glands, in their structure identical with each other. It will 

 be most convenient, in studying the intimate structure of 

 the gland, to begin at the nipple and follow out one of the 

 ducts to the termination of its branches in the secreting 

 culs-de-sac, 



The canals which discharge the milk at the nipple are 

 called lactiferous, or galactophorous ducts. They vary in 

 number from ten to fourteen. The openings of the ducts at 

 the nipple are very small, measuring only from -fa to ^ of 

 an inch. As each duct passes down, it enlarges in the nipple 

 to -fa or -^ of an inch in diameter, and beneath the areola 

 presents an elongated dilatation, from -J- to J of an inch in 

 diameter, called the sinus of the duct. 1 During lactation a 

 considerable quantity of milk collects in these sinuses, which 

 serve as reservoirs. Beyond the sinuses the calibre of the 

 ducts is from -fa to -J- of an inch. They penetrate the differ- 

 ent lobes, branching and subdividing, to terminate finally in 

 the collections of culs-de-sac which form the acini. Most 

 modern observers are agreed that there is no anastomosis be- 

 tween the different lactiferous ducts, and that each one is 

 distributed independently to one or more lobes. 



1 KOLLIKER, Handbuch der Gewebelehre des Afenschen, Leipzig, 1867, S. 571. 



