560 THE PHYSIOLOGY OF REPRODUCTION 



theory the colostrum corpuscles were the detached epithelial 

 cells. In opposition to this theory, it has been pointed out 

 that there is no evidence of the extensive cell multiplication, 

 such as would be required in order to supply the large number 

 of cells which, according to this hypothesis, would necessarily 

 become detached. Heidenhain * has shown that if this theory 

 is correct, the cells of the gland must be completely renewed as 

 often as five times in one day in order to provide the solid 

 constituents of the secretion. 



The second of the above-mentioned theories receives con- 

 siderable support from the circumstance that it has the analogy 

 of the great majority of secretory glands. 2 Moreover, the recent 

 investigation of Bertkau 3 points strongly to the conclusion that 

 any appearances of disintegration which the secretory cells 

 possess is due to imperfect fixation. This author states that he 

 found no necrobiosis of any kind in these cells, and he believes 

 that milk formation is a purely secretory process. The colostrum 

 corpuscles, according to those who hold this view, are of the 

 nature of wandering leucocytes. 



The third theory was first suggested by Langer, and has 

 since been adopted, with various slight modifications, by 

 Heidenhain, 4 Steinhaus, 5 and Brouha 6 and others. According 

 to their view the 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 constitu- 

 ents of the milk. The fat droplets which collect in the disintegrat- 

 ing part of the cell give rise to the milk fat. The basal portions of 

 the cell remain in position without being detached, and subse- 

 quently develop fresh processes, which in their turn become 



1 Heidenhain, " Die Milchabsonderung," Hermann's Handbuch der Phy- 

 siologie, vol. iv., 1883. 



2 Schafer, loc. cit. 



3 Bertkau, " Ein Beitrag zur Anatomic und Physiologie der Milchdruse," 

 Anat. Anz., vol. xxx., 1907. 



4 Heidenhain, loc. cit. 



5 Steinhaus, " Die Morphologic der Milchabsonderung," Arch. f. Anat. 

 u. Phye., Phys. Abth., Suppl., 1892. 



6 Brouha's paper (loc. cit.) contains a full account of the literature. 



