i2 4 THE HUMAN SPECIES 



and provided with cartilage cells man is also without the solid 

 plate of lingual cartilage and the lingual tuberosity of the car- 

 nivora, commonly known as a condensation of the mucous 

 membrane with glands and macroscopically large papillae. 1 



Those glands in the worms which open into the small intes- 

 tine, similar glands in the turbellaria, the groups of glandular 

 cells in the anterior extremities of the body in the trema- 

 toda, the glandulous formations in the so-called pharynx of 

 the trematodes and nematodes, and the single-celled glands in 

 the proboscis and jaws of the hirudinea, must be considered 

 as belonging to the salivary type of secreting structure. In 

 some classes of the arthropoda the salivary glands are either 

 absent or very slightly developed, and they vary in develop- 

 ment in the crustaceans, arachnida, myriapoda and insecta. 

 Of the molluscs, only those classes provided with a head, 

 namely, the gastropoda and cephalopoda, possess salivary 

 glands. This fact is unfavourable to the theory that the pos- 

 session of salivary glands is connected with an existence on 

 land, as has been asserted from the absence of these glands in 

 the fishes. In this respect, the amphibians and the majority 

 of the reptiles occupy undoubtedly a higher place in the scale, 

 though here the mucous glands are of first importance (Wieder- 

 sheim). The salivary glands are most highly developed in 

 vipers and adders, three pairs of salivary glands in addition to 

 their mucous glands being usually present. In birds the salivary 

 glands occur at the angle of the lower jaw (corresponding to 

 the sublingualis of the mammals), in the angle between the 

 two jaws (corresponding to the Parotis), and in the triangular 

 space beneath the before-mentioned glands (corresponding to 

 the submaxillaris). 



The parotid gland is in man, and in most of the mammals, 

 a purely serous (albumen secreting) gland. Only in the dog 

 does the Parotis possess oblong cavities with mucous-secreting 

 cells. 



The sublingual gland is in man and in most of the mammals 

 a true mucous gland. In the pig and carnivora this gland 

 appears combined with lobes for the secretion of serum. 



Lastly, the submaxillary gland in man and all the mammals 



1 Ellenberger, loc. cit., p. 654. 



