Joseph Marshall Flint 291 



out, the thick, ropy, tenacious secretion of the mucous alveoli is partly 

 expelled from the alveolus into the ducts by the assistance of the me- 

 chanical action of this elastic membrane. He did not suggest, however, 

 the interesting corollary that, in the secretion of this substance, the 

 elastic tension of this same mebrane must be overcome, which means 

 that secretion in the mucous alveoli must at least be accomplished under 

 a sufficient jjressure to overcome this elastic tension. It is, of course, 

 well known that secretion takes place under a pressure higher than that 

 of the blood, and this, together with the recent work which seems to 

 indicate that the osmotic pressure within the cell is twenty times greater 

 than the blood pressure, would explain how the stretching of this 

 elastic membrane could be easily accomplished during the activity of the 

 glandular cells. 



There are several characteristic staining reactions of the duct epithe- 

 lium which can be observed with more or less distinctness from the Duc- 

 tus submaxillaris to the alveoli. The duct cells take the ordinary con- 

 trast stains deeply. They exhibit especially a peculiar affinity for congo 

 red. x\ccordingly as in the case of demilunes of Gianuzzi, congo red may 

 almost be considered as the special selective stain for the duct epithe- 

 lium. When elastic tissue preparations are made and contrasted with 

 picric acid the epithelial cells of both intra- and extralobular ducts take 

 a rather yellowish-green tint, while the rest of the epithelium is ouly a 

 pale yellow (Fig. 7). In Van Gieson preparations or modifications 

 of this method the duct epithelium stains a pale yellow while the serous 

 alveoli are a deep purple and the mucous alveoli stain a dark blue. 



Discussion' of the Literature. 



Comparatively little work has been done upon the ducts of the sali- 

 vary glands alone, most of the research appearing as collateral study in 

 course of work upon other portions of the organs. Yon KoUiker ' states 

 that the ducts of the salivary glands are made up of a single layer of 

 cylindrical epithelium which is surrounded by connective tissue and 

 some elastic fibres. Those about the D. submaxillaris according to 

 Kolliker are arranged in the form of a double membrane. As we have 

 seen, however, there is just one well-marked elastic membrane located 

 external to the membrana propria and several concentric, less regularly 

 arranged lamellae situated external to the regular elastic tunic. It was 

 one of these, no doubt, which von Kolliker believed was the second 

 elastic sheath. He states, moreover, that this double arrangement of 



9 Kolliker: Gewebelelire. Bd. ii, Leipzia:, 1852. 



