THE MAMMARY GLAND. 449 



to concede in all respects the correctness of Creighton's inter- 

 pretations. The evidences of epithelial destruction for purposes 

 of milk secretion, are not positive and convincing. In the Har- 

 derian gland, as well as in the mamma, we have observed the 

 extrusion of fat-droplets from cells replete with them without 

 destruction of the cell itself. Partsch agrees with us in assum- 

 ing that the cells may burst or otherwise discharge their con- 

 tents, and yet retain enough protoplasm to maintain their vital- 

 ity ; and also that the vital contractions of the protoplasm 

 may force out the oil-globules without destruction of the epi- 

 thelium. What Creighton has called vacuolation does not mean 

 death to the cells concerned in this action, for they retain their 

 nuclei and sufficient protoplasm to become re-established as 

 perfect epithelia. That this reformation of old epithelium 

 takes place, is proven by the fact that a new formation by 

 proliferation has never been observed, and by the additional 

 circumstance that the mammary acini never show more than 

 a single layer of lining-corpuscles, and, moreover, always show 

 this layer complete. 



In this, as in many other respects, the mamma closely re- 

 sembles the Harderian gland, more particularly of the roden- 

 tia, as described by one of the writers in a monograph. The 

 basement-membrane of the acini in every particular also corre- 

 sponds in the two kinds of glands, being in both a homoge- 

 neous, apparently structureless membrane, with superimposed 

 branched adventitial cells, the so-called Stutzzellen of German 

 writers. A basket-shaped reticulum, such as has been described 

 by Boll, Langer, Kolessnikow, Moullin, and others, is never 

 found to constitute this membrana propria, although artifi- 

 cially, appearances simulating a structure of this kind are 

 readily obtained, and have been interpreted by several histolo- 

 gists as natural occurrences. 



In the cutaneous sebaceous glands the secreting vesicles are 

 filled with several superimposed layers of epithelia, and it is 

 this circumstance which leads to an entirely different mode 

 of secretion. For there it would indeed appear that the cells 

 undergoing fatty degeneration become detached from their 

 bases and find their way into the narrow lumen of the acinus. 

 The older or inner generation of cells thus vanishing is replaced 

 by new corpuscles formed by gradual proliferation from the 

 peripheral zone. 



