388 



THE DIGESTIVE SYSTEM 



Stb'hr, that the demilunes represent an inactive, the mucous cells, an 

 active phase of mucus secretion. The easy demonstration of inter- 

 mediate stages in many mucus-secreting glands lends strong support to 

 this theory, and in the present state of our knowledge it seems beyond 

 doubt that such a process actually occurs in at least some of the mucus- 

 secreting glands. 



A third theory, more recently advanced by Solger (Anat. Anz., 1894) 

 and stoutly supported by Krause (Arch. mikr. Anat, 1895, 1897, and 

 1901) and others, considers the demilunes to be 

 true secreting cells which form a serous secre- 

 tion and are therefore functionally independent 

 of the mucinous cells. This theory receives 

 strong confirmation in the fact first observed 

 by Cajal (1889) and since that time repeatedly 

 demonstrated, that the demilunes, like the true 

 serous cells, are provided with a system of in- 

 tercellular secretory canaliculi by which they 

 are placed in relation with the glandular lumen. 

 Moreover Krause was able to demonstrate that 

 granules of sodium indigo sulphate were se- 

 creted by these cells, as also by the true serous 

 cells and the striated epithelium of the intra- 

 lobular ducts. 



The mucus-secreting cells examined in the 

 fresh state present a clear, highly refractive 

 appearance. They closely resemble the typical 

 goblet cells, but instead of being isolated among 

 the granular serous cells, they may invest the 

 entire acinus, or even the whole of a small 

 lobule may contain only mucus-secreting cells. 



After the customary preparation by fixation and staining, the mu- 

 cous cells present a coarse basophilic reticulum which occupies the distal 

 portion of the cell. Coarse granules, with proper fixation and in fresh 

 tissue as well, can be demonstrated within the meshes of the reticu- 

 lum. These granules are readily colored by the so-called specific mu- 

 cus stains (Mayer's muehematein and mucicarmin, safranin, and thio- 

 nin). 



In the mucous cells the nucleus is crowded to the base or proximal 

 end of the cell and flattened against the basement membrane. It is sur- 

 rounded by a small remnant of finely granular cytoplasm, which, after 



FIG. 358. Mucous ACINI 

 OF THE RETROLINGUAL, 

 GLAND OF THE RAT. 



The ducts and secretory 

 capillaries have been black- 

 ened, r, demilunes with 

 secretory capillaries; s, 

 mucous cells. Golgi meth- 

 od. X500. (After K61U- 

 ker.) 



