478 THE SALIVARY GLANDS. 
nmco-albuminous glands, mixed glands, albumino-mucous glands, demilune 
glands, mucous glands. 
The demilune cells, there can be little doubt, are albuminous 
secretory cells. 1 If we compare a series of submaxillary glands, passing 
from albuminous to mucous, we find that the albuminous cells become 
more and more confined to the ends of the terminal tubes, and the fewer 
there are the more compressed they become by the mucous cells, a 
feature, however, which is more marked in hardened than in fresh 
glands. And when the gland secretes, the demilune cells show obvious 
signs of secretory activity. The small discrete granules in them 
diminish in number, and in some animals form an inner granular zone; 
in alcohol-hardened glands, the demilune cells stain more deeply with 
carmine, and the nuclei and nucleoli are more conspicuous. The cells 
diminish in size after prolonged activity of the gland. In the earlier 
stages of secretion they appear to be larger, but this is probably due to 
a diminution in the size of the mucous cells, and so of the whole tube, 
whereby the demilune cells are less flattened. 
A comparison of the large salivary glands in different mammals 
shows that the parotid has least variation in structure, and the sub- 
maxillary gland the most. 
The parotid gland, as a rule, contains albuminous cells only; but 
in the dog there are commonly, if not always, a few mucous cells, 
or mucous alveoli present. And there may be in the dog a small 
mucous lobule, pouring its secretion into the duct a short distance from 
the main gland. 
The submaxillary glands are entirely albuminous in rodents. In 
primates, the majority of the cells are albuminous, but some are mucous. 
In solipedes and ruminants, the glands are " mixed," but most of the 
cells are mucous. In carnivora the great majority of the alveolar cells 
are mucous, but some are albuminous, and there are fewer albuminous 
cells in the submaxillary gland of the dog than in that of the cat; 
thus in a microscopical preparation of the gland of a dog, the albuminous 
cells are almost entirely in the form of demilunes, whilst in a similar 
preparation of the gland of a cat, a considerable number of albuminous 
alveoli are seen. In the mole, large portions of the submaxillary gland 
do not even contain demilunes, and in these portions none but typical 
mucous cells occur. 
The sublingual gland in all animals contains a greater or less 
proportion of mucous cells, and it is in consequence generally called 
a mucous gland. But as it always contains albuminous cells also 
it belongs properly to the class of mixed glands. The sublingual gland 
has certain characters which distinguish it from the submaxillary gland. 
It is more obviously tubular, the lumina are often large, the cells in a 
section of a hardened specimen are more columnar, and a considerable 
number of them consist, in their ordinary resting state, of proteid 
material in the outer third, half, or even two-thirds, and of mucous 
material in the remaining portion next the lumen. 
The orbital gland 2 of the dog is mucous, the mucous cells are large and 
contain very little proteid substance, the demilunes are much flattened. The 
1 Langley, Trans. Interned. Med. Cong., 1880 ; Proc. Roy. Soe. London, vol. xi. p. 
364 ; and this view lias been taken by most subsequent observers. 
2 Cf. Lavdowsky, Arch. f. mikr. Anal., Bonn, 1877, Bd. xiii. p. 288. 
