408 



ANATOMY OF VERTEBRATES. 



The buccal arc smaller than the labial glands, but resemble 

 them in form and position, being irregularly spheroidal, and 

 placed between the buccinator and mucous membrane ; they open 

 by the orifices of distinct ducts upon the free surface of the latter. 

 The molar glands are placed between the buccinator and masseter 

 muscles. They are larger and more dense than the buccal, 

 being composed of several lobes. The ducts open upon the 

 mucous membrane at the posterior part of the cheek. The pala- 

 tine glands are very numerous and small, and situated partly 

 between the mucous membrane and the palatine arch, and partly 

 between the mucous and muscular layers of the soft palate. 

 The former are situated on either side of the median line, and 

 form a thick layer, being more closely aggregated together in the 

 front and behind than in the middle, opening on to the mucous 

 membrane by distinct orifices. The latter, smaller than the 

 former, exist both on the upper and lower surface of the velum, 

 and are continuous below, where they are more numerous than 

 above, with the glands of the hard palate. The aggregate follicles 

 opening near the fossulate papillae at the back part of the tongue 

 are sometimes specified as the ( posterior lingual glands.' Like 

 the other subsidiary glands their secretion is more mucous and 

 lubricating than solvent : and the homologues of most of these 

 glands are maximised in 

 herbivorous Mammals in 

 relation to the movements 

 and mastication of their 

 coarse vegetable food. 



The diversion of the paro- 

 tid secretion from the mouth 

 of a horse, during mastica- 

 tion of oats, was followed 

 by dryness of the interior 

 of the bolus and an exte- 

 rior envelope of tenacious mucus, which was as abundant as be- 

 fore the division of Steno's ducts ; the experiment } indicating 

 that the secretion of the parotid is of the more fluid saliva which 

 moistens, in ordinary mastication, the whole mass ; and that the sub- 

 maxillary and sublingual, like the more diffused tributary glands, 

 provide the secretion of the slimy lubricating saliva. Further 

 experiments showed 2 that the flows from the parotid, sub- 

 maxillary and sublingual glands are respectively regulated by 

 conditions special to each. Thus, the quantity of saliva secreted 





Anterior lingual gland, Human, nat. size. cxxv". 



1 cxxvi". 



Ib. 



