43 The Submaxillary Gland 
[o4) 
mucous cells in various stages of activity, speaks of the false or pseudo- 
lunulae, classifying among the latter Pfliiger’s demilunes, which are the 
peripheral protoplastic portions of unfilled mucous cells and membrana 
propria demilunes consisting of sections of thickened basement mem- 
branes. Another poiut which has given rise to considerable discussion 
is the stratification of the alveolar epithelium, many authors holding 
that the cells are arranged in two layers while others maintain that only 
a single layer exists. The conditions probably differ in different ani- 
mals. In man, apparently, both groups of cells, central and parietal, 
touch the basement membrane, while in pigs it is not uncommon to find 
even in the adult many mucous cells separated from the basement mem- 
branes by demilunes. The chief point of interest in this connection, 
however, is the fact that the two groups develop from a double layer of 
epithelium. 
The significance of the demilunes has been the point of several theo- 
ries that have given rise to more or less discussion. Among the promi- 
nent ones are the “ Ersatztheorie ” of Haidenhain, “ Phasentheorie” of 
Stéhr and the doctrine of the specificity of the demilunes suggested by 
von Ebner. 
The “ Ersatz” theory is based on the idea that there are two groups 
of cells, a central group with the characteristic arrangement which con- 
sists for the most part of mucous cells and a peripheral group corres- 
ponding to the demilunes which through mitosis increase and undergo 
a mucous metamorphosis to replace the destroyed cells of the central 
group. Against this theory, however, the following objections are 
made by Oppel: 
1. That the mucous cells are not destroyed or disintegrated during 
the secretion. 
2. Pure mucous glands without demilunes are known to exist. 
3. The demilunes never show mitotic figures. 
The “ Phasentheorie ” is based on the assumption that the mucous and 
parietal cells are merely different functional stages of the same elements. 
Stohr and others believe that the mucous cells are not destroyed during 
the secretion of the gland but persist like the cells of the stomach epi- 
thelium and that the parietal cells represent the peripheral proto- 
plasmic part of the mucous cells which are not transformed into mucous 
globules. Supporting this fact are the pictures obtained during the 
various stages of activity of the gland, which seem to suggest, according 
to these authors, that the cells at first have a round nucleus with only 
the central portion of the cell next to the lumen transformed into 
mucous. As the production of this substance increases, the nucleus is 
