ORGANS OF DIGESTION. 407 



along the sides of the mouth in mammalia, which form large 

 conglomerate buccal glands in several herbivora, assist the 

 salivary glands in softening the food while thus delayed for 

 mastication, and many species of quadrumana, cheiroptera, 

 rodentia, and the ornithorhyncus have cheek-pouches, like 

 the crop of birds and the paunch of ruminantia, to collect 

 the food before mastication. The parotid, submaxillary and 

 sublingual salivary glands, so generally developed in mam- 

 malia, are largest in herbivorous quadrupeds where the 

 coarse food is longest subjected to mastication, less in car- 

 nivorous species where it is more quickly divided and swal- 

 lowed, and least in the aquatic tribes where the thin limpid 

 secretion of these glands is rendered less necessary by the 

 moist condition of their food. The velum palati is more ex- 

 tensive than in the former classes ; but the uvula is rarely 

 developed, excepting in the highest quadrumana and man, 

 and the cutaneous papillae, so commonly spread over the 

 tongue and palate, sometimes, as in the monotrema, acquire 

 the density of spines in their cuticular sheaths, as they do 

 in many birds. The tongue is supported by the short, 

 broad body of the os hyoides, and sometimes a vermiform 

 median fibre-cartilage, and the two pairs of cornua are most 

 developed in the herbivorous quadrupeds, where the ante- 

 rior pair reach the large styloid bones. The os hyoides, in 

 its most perfect form, consists, as shown by Geofiroy, of 

 twelve elements, the body of the bone being composed of a 

 glosso- and a basi-hyal piece, the anterior cornua consisting 

 each of an apo- a cerato- and a styl-hyal element, and the 

 smaller posterior cornua containing each an ento- and a 

 uro-hyal bone, and this complicated condition of the os 

 hyoides, common in the ruminantia, is sometimes found as 

 an abnormal form of that bone in man. But the cornua, 

 in the normal state, are least developed in man and the 

 orangs, and no trace of them is seen in the manis. 



The pharynx of mammalia forms a distinct and wide cavity, 

 and the long cylindrical oesophagus, corresponding with the 

 length of the neck, never presents an ingluvial dilatation 

 above the sternum, as it does in so many birds. The resopha- 

 gus is wide and dilatable in the carnivorous tribes, where the 

 food is commonly swallowed in masses, and it is more nar- 

 row and muscular in the herbivorous quadrupeds, where 



