168 Finer Structure of the Glandula Submaxillaris 
thin sections (2-4 micra), he was able to demonstrate certain structural 
differences in these two cell complexes. The cells of the darkly stained 
areas showed a cytoplasm filled with large, deeply stained granules. 
In some cases the granules filled the entire cell, while in other cells 
could be seen a lightly stained, fibrillar network, within the meshes of 
which the distinctly colored granules were held. The “ transparent 
gland tubules” he found to consist of cells, the cell substance of which 
was formed of a fine network with thickened nodal points, forming 
regular clear spherical meshes. This second variety of cell did not fix 
so readily nor so well as the granule-holding cell and was frequently 
found shrunken and with irregular meshes, while at other times, under 
better conditions of fixation, the meshes appeared as only the expression 
of clear, round, unstained granules separated from one another by the 
colored network. Apart from cellular structure he believed that these 
two cell groups differed in no way from each other. “ Only,” he added, 
“it must be mentioned, that the deeply stained tubules are found gen- 
erally near an intercalated duct.” To this rule, however, he claimed 
exceptions. 
In order to explain the occurrence of these two varieties of cell forms, 
Miiller considered two possibilities. Either the two forms of cells were 
of different kinds and yielded different secretions or they were identical 
and elaborated the same secretion, the apparent differences in structure 
resulting from different stages of activity. The second view appeared 
to him to be the correct one. There was not, he believed, a difference 
in kind between the cells but a difference in the state of function. Ex- 
perimental evidence derived from an artificial stimulation of the gland, 
seemed to him to substantiate his opinion, when he found that after 
active. secretion, the deeply colored areas of the gland parenchyma under- 
went a change as the granules disappeared. Here he was able to find 
transition stages between the light and dark cells. In case these granules 
might be simply artefacts in the sense of Fischer, he examined fresh 
tissue and found a similar and even more striking condition of differ- 
entiation between clear and dark cell areas, and furthermore that both 
kinds of cells contained granules, those of the dark areas being more 
highly refractive. 
In the light of these observations, he formulated an hypothesis of 
the process of secretion of saliva in this gland. According to his view 
the cells of the clear areas contained the finished products of secretion. 
The unstained granules in these cells were transformed into the secretion 
vacuoles and these discharged their contents as saliva into the secretion 
