LACTATION 593 



cells of the gland lengthen out, so that their ends come to project 

 freely into the lumina of the alveoli. The projecting portions then 

 undergo a process of disintegration before or after becoming detached, 

 and the cell substance passes into solution to form the albuminous 

 and carbohydrate constituents of the milk. The fat droplets which 

 collect in the disintegrating part of the cell give rise to the milk fat. 

 The basal portions of the cell remain in position without being 

 detached, and subsequently develop fresh processes, which in their turn 

 become disintegrated. It is believed, however, that some cells simply 

 discharge their fat droplets and other contents into the lumina, while 

 otherwise remaining intact.i 



Steinhaus states that mitotic division of the cell nuclei in the 

 actively secreting mammary glands is of frequent occurrence, and 

 that the daughter nuclei which lie in the outer portions of the cells 

 degenerate and share in the general process of dissociation. Szabo ^ 

 also records the occurrence of two or more nuclei in the same cell 

 during lactation, and similar evidence of nuclear division has been 

 observed by others. Moreover, it is argued that this view is in. no 

 way inconsistent with the generally accepted homology between the 

 mammary and sebaceous glands, since it is easy to understand how, 

 in the course of evolutionary development, the mode of secretion in 

 the glands in question might have undergone an alteration, whereby 

 the process of disintegration in the actively secreting cells became 

 gradually lessened as' the character of the secretion changed. On 

 the other hand, if we suppose that the cells of the mammary gland 

 merely extrude their secreted materials without undergoing any 

 histological disintegration, it is more difficult to uphold the homology 

 in question. Lastly, it should be mentioned that those who, like 

 Steinhaus, support the theory of partial disintegration, do not regard 

 the colostrum corpuscles as detached epithelial cells, as Heidenhain 

 did, but agree with those who uphold the purely secretory theory in , 

 supposing the corpuscles to be of the nature of "mast cells," or 

 basophil leucocytes which have wandered inward from the connective 

 tissue of the gland, as already described, and have made their way 

 into the lumina of the alveoli.^ 



1 Brouha, loc. cit. ; also " Les Ph6nomeiifes histologiques de la Secretion 

 lactfe," Anat: Am., vol. xxvii. 



^ Szab6, " Die Milchdrtise im Euhezustande und wahrend ihrer Thatigkeit,' 

 Arch.f. Anat. u. Phys., Anat. Abth., 1896. 



' For references to further literature upon the physiology of milk formation 

 see Basch,. "Die Physiologie der Milohabsonderung," Ergeb. des Phys., 1903, 

 Jahrg. See also the following for references to the histology : Bizzorzero 

 and Ottolanghi, "Histologie der Milchdruse," Merkel and Bonnet's Ergeb. d. 

 Anat. u. Entmck, vol. ix., 1900, and von Ebner, "Von den Geschlechtsorganen," 

 Kolliker's Handbuch der Oewebelehre des 3fenschen, vol. iii.-, 1902. 



