Joseph Marshall Flint . 439 
pushed more and more toward the periphery of the cell, where, with the 
remainder of the untransformed protoplasm, it rests against the base- 
ment membrane. ‘These with similar neighboring cells form the parie- 
tal group. In extreme cases the nuclei may be pressed flat against the 
base of the cell. Miiller raises the following objections to Stohr’s 
theory: 
1. The demilunes are not empty of secretion but contain secretion 
granules. - 
2. Intermediate stages between filled mucous cells and demilunes do 
not exist. 
3. The secretion capillaries described by Stéhr with the Golgi method 
are simply intercellular spaces, while true demilunes have distinct intra- 
cellular secretion canaliculi. 
The doctrine of the specificity of the demilunes suggested by v. Ebner 
is based upon the following conclusions : 
1. The cells of this group contain secretion granules. 
2. They contain secretion canaliculi which may be demonstrated by 
the Golgi method. 
3. Certain substances injected into the circulation of living animals 
are demonstrable in the demilunes or their secretion canaliculi. 
4. They react distinctly to certain microchemical tests. 
From the study of the development of the demilunes in the submax- 
illary gland in a series of embryo pigs, it becomes patent that the doc- 
trine of the specificity of the demilunes is the only one which is at all 
tenable. Aside from the various conclusions given by Miiller support- 
ing this fact, the indisputable evidence of their ancestry shows that, 
throughout the period of embryonic life, they are cells of an individual 
specific group, derived from the peripheral layer of epithelium in the 
embryonic alveolus. They maintain their identity throughout life and 
represent neither young cells which undergo, at a later period, transfor- 
mation into the mucous cells of the alveolus, nor one of the functional 
stages of the mucous group. Embryologically and anatomically they are 
definite units and must be considered as cellular complexes which form 
definite structural elements of the alveoli of certain of the salivary 
glands. 
CHANGES IN THE Duct EPITHELIUM. 
In a pig +4 centimeters long the main ductus submaxillaris is already 
composed of two layers of cells which are cubical in shape and not dis- 
tinetly columnar. These can be followed in the main divisions of the 
ducts and terminate in the solid buds that form the apices of the grow- 
