262 DIGESTION 



We meet with similar phenomena in fresh preparations of the mucous 

 glands. A gland from the tongue of Rana esculenta teased in a 0.6-per-cent 

 salt solution (Biedermann) almost always shows cells, which in the ends 

 turned toward the lumen are thickly set with dark, strongly refractive gran- 

 ules. When the same object is observed in active secretion the dark granules 

 have disappeared for the most part, or form only a narrow border along the 

 inner edge of the cells. The latter contain also clear, vacuolar drops 

 (Fig. 102). 



From these observations it appears that in the albuminous as well as in the 

 mucous glands, a substance is formed during the resting state, which in the 

 fresh gland has the form of small granules. This substance is liberated from 

 the cells in the act of secretion and as a consequence the cells decrease in size, 

 especially after a copious discharge; the main part of the cell is now clear. 



Are the specific constituents of the secretion derivatives of the living proto- 

 plasm, or are they to be regarded as products of its activity? This question 

 cannot be answered definitely at present. Heidenhain conceived that in the 

 mucous glands at least the cells as a whole are converted into the secretion, and 

 that the so-called demihime cells of Gianuzzi are young cells destined to replace 



FIG. 102. Parts of a tongue gland of the frog (Rana esculenta), fresh condition, after Bieder- 

 mann. A, resting state. B, after stimulating the glossopharyngeal nerve for three hours. 



the mucous cells after their disintegration. This assumption however is not in 

 accord with the fact that cell divisions are very rarely met with in secreting 

 glands. That cells do occasionally perish in very active secretion and can be 

 replaced by division, has nothing whatever to do with the process of secretion 

 as such. And as for the demilumes, they appear from recent researches (Stohr, 

 Noll) to be simply empty mucous cells. 



Other investigators, with Altmann at their head, regard the granules as 

 morphological derivatives of formed constituent elements, and claim that the 

 manner of their origin, their growth and their transformation indicate that they 

 are vital units. 



From all that we know, however, the granules found in the resting gland 

 might just as well represent products of the metabolic activity of the proto- 

 plasm; hence no destruction of living substance would be involved in their for- 

 mation. The material at hand is by no means sufficient to decide a question 

 fundamentally so important. 



