458 THE SALIVARY GLANDS, .BY E. F. W. PFLUGER. 



Heidenhain draws the conclusion from these facts, that the 

 first form are disintegrated in the act of secretion, whilst the 

 second are newly developed. 



There still remains the possibility that the " mucous cells," 

 in consequence of their persistent activity, have undergone an 

 essential alteration in their chemical constitution, to which 

 the differences in their appearance are attributable, accord- 

 ing to whether they have been at rest or long in action. I 

 cannot, however, deny that the completely different appearances 

 (see fig. 95) presented, strongly support Heidenhain's opinion. 



Heidenhain lastly adduces, in support of his opinion, the 

 circumstance that he was able to isolate a larger number of 

 cells undergoing fission from the excited gland, after macera- 

 tion in iodized serum, than in that which has been kept at 

 rest. The epithelial cells of the salivary glands of the dog 

 are generally isolated with difficulty. The isolation of the 

 younger cells in the excited gland may perhaps be facilitated 

 by this very excitation rendering them looser, softer, and more 

 watery, as Heidenhain himself remarks. May not also the 

 continuous streaming of saliva, rich in the corroding carbonate 

 of soda, favour their isolation ? It is further noticeable that, 

 according to Heidenhain, these young cells, after long macera- 

 tion, become isolated sooner than other kinds of epithelia, 

 showing that, under favourable circumstances, they are formed 

 earlier or in larger numbers. I must further observe, that, in 

 accordance with my experience, I can demonstrate in every 

 quiescent salivary gland thousands of epithelial cells in the act 

 of multiplication. The sublingual gland of the rabbit is particu- 

 larly well adapted for this purpose, offering the additional advan- 

 tage that, like the submaxillary gland of the dog, it exhibits 

 large and beautiful mucous cells and semi-lunar bodies. In any 

 such gland, thousands of young epithelial cells, developing by 

 the process of gemmation, may be discovered. I hold a gradual 

 process of disintegration of the alveoli to be highly probable, 

 on the ground of that regeneration of salivary cells which I 

 discovered to proceed from the cylinder cells of the excretory- 

 ducts. The question as to how far the nervous system exerts 

 a primary or a secondary influence on this vegetative process 

 still demands further investigation. 



