478 THE SALIVAR Y GLANDS, 



muco-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 tre 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. Internal. Med. Cong., 1880 ; Proc. Roy. Soc. London, vol. xi. p. 

 364 ; and this view has been taken by most subsequent observers. 



2 Cf. Lavdowsky, Arch. f. mikr. AnaL, Bonn, 1877, Bd. xiii. p. 288. 



