OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 145 



and resemble then in all respects the alveoli of true salivary 

 glands, or the so-called serous glands known through A. Heiden- 

 hain and von Ebner (see further below). They are always in 

 connection with a tube given off by one of the salivary ducts 

 with rod- epithelium {i. e. Piliiger's " Speichelrohreu ") and lined 

 with short pavement epithelium. In some parts it is also seen 

 that in the above alveoli with " granular " epithelium, one or 

 two of the cells are already mucous cells, but the whole alveolus 

 is much smaller than an ordinary one. There can be little doubt 

 that in the submaxillary gland of half-grown dogs (I worked 

 with animals six to eight months old) there exists a certain 

 amount of unripe gland-structure, but in different stages of de- 

 velopment, consisting of intermediary forms between more or 

 less solid chain-like masses, composed of polygonal uninuclear 

 " granular ^'^ cells, then groups of such cells around a small 

 lumen, and finally such forms in which some of the " granular " 

 cells are replaced by " mucous cells." 



Pliiger mentions that in the resting submaxillary glands of 

 rabbits there are " thousands " of young cells, developing in 

 connection with the rod-epithelium of the salivary ducts. Lav- 

 dowsky denies this, and says that Pfliiger probably mistook the 

 aggregate of cells constituting the " crescents " for developing 

 cells. Although I have not been able to see in the resting 

 submaximillary gland of dog anything like the cells that Pfliiger 

 delineates,^ I must oppose Lavdowsky's statement as regards the 

 non-existence of developing cells in any but stimulated glands. 

 As I have pointed out above, there is a perceptible amount of 

 gland tissue, in the half-grown dog, just passing through the 

 different stages of development. 



The above intermediary forms between alveoli in which some of 

 the " granular " cells have changed into mucous cells and alveoli 

 entirely composed of "granular" cells distinctly shows us the 

 relation that exists between the mucous cells and the "granular" 

 cells of the crescents. This relation coincides entirely with 

 that stated by Heidenhain and Lavdowsky for the exhausted 

 gland, viz, that the parietal cells, or the cells of the crescents give 

 origin to the mucous cells. That this is the relation in the 

 growing parts of the gland, of this I have no manner of doubt, 

 but I have likewise no doubt that while the suhmaxillary gland 

 is in a normal state of function, such as is represented in the 

 ordinary life of the animal, the ^'mucous cells," as a ivhole, are 

 not destroyed during secretion, and that, therefore, there is no 

 need for their being regenerated from the parietal cells. I must 



' I use the word " granular" as indicating the appearance of the substance 

 of the parietal cells, but of course I have stated above that these granules are 

 only apparent, that substance being in reality a dense network of fibrils. 



' Strieker's ' Handbook,' fig. 93— 95, 



