356 THE DIGESTIVE APPARATUS IN MAMMALIA. 



buccal opening ; followed from this point into the interior of the cavity it 

 lines, it is seen to spread itself at first over the internal surface of the lips, 

 then to be prolonged backwards on the cheeks as far as the posterior pillars 

 of the tongue. If it is examined above and below, to the bottom of the 

 groove which corresponds to the point of insertion of the lips and cheeks, 

 it is seen to cover the maxillary bones and envelop the base of the teeth, 

 where it constitutes the gums. From the superior dental arcade, it extends 

 over the palatine arch and the soft palate. And from the inferior arcade, 

 it descends to the floor of the mouth, and is reflected over the tongue to form 

 a covering for that organ. At the isthmus of the fauces it is continuous 

 with the pharyng<|il mucous membrane. 



The organisation of the mucous membrane of the mouth is perfectly in 

 harmony with the digestive acts performed in that cavity. It is there 

 where the alimentary substances, which are sometimes very hard, very 

 resisting, and covered with asperities, are crushed ; and to escape inevitable 

 injury, this membrane is protected by a very thick epidermis in those places 

 which are most particularly exposed to the contact of these substances, such 

 as the upper surface of the tongue, the palate, and the cheeks ; even the 

 corium or sub-epidermic layer, is also greatly thickened. But nature has 

 not made this provision for the parts which are removed from the direct 

 contact of alimentary matters ; as, for example, on the lateral aspects of 

 the tongue, where the buccal membrane is delicately organised. 



This membrane also shows, in its lingual portion, small organs for the 

 gustation of savours, the perception of which is one of the most important 

 preparatory acts of the digestive functions ; as the sensation resulting from 

 this appreciation constitutes an excitant to the desire for food, and also 

 informs the animal of the good or bad properties of the substance introduced 

 into the mouth. 



DIFFERENTIAL CHARACTERS IN THE MOUTH OF OTHER THAN SOLIPED ANIMALS. 



That the different regions of the mouth in the domesticated animals should offer some 

 diversities will be readily conceived, as all are not submitted to the same regime, nor do 

 they all live in the same manner. 



BUMINANTS. 1. Lips. The lips of the Ox are remarkably thick and rigid, and 

 possessed of but little mobility, notwithstanding the great development of the muscles 

 that move them ; so that they only concur indirectly in the prehension of food, the 

 tongue being charged with the largest share in this important task. The upper lip 

 offers in the middle of its external surface a large patch destitute of hair, variously 

 coloured in different animals, always humid in health, covered by small depressed 

 eminences, and perforated by minute apertures, through which the secretion of numerous 

 thick, yellow, subcutaneous glandules passes to the surface. This space, situated 

 between the two nostrils, constitutes the muffle. (Around the muffle are a few hairs 

 sometimes, of the nature of tentaculse.) 



In the Sheep and Goat the lips are thin and very mobile, and take an active part in 

 the prehension of food. The upper lip does not show any muffle, and is divided into 

 two portions by a median groove. In the Sheep this groove is in reality a fissure ; so 

 that each half of the lip can be readily moved independently of the other. (The upper 

 lip is covered with hair in both animals. The Goat has a long tuft of hair appended to 

 its lower lip, the beard.) 



2. Cheeks. On the inner surface of the cheeks in the Ox, Sheep, and Goat, from the 

 commissure of the lips to the first molar tooth, is a multitude of long, thick, conical 

 papillae directed backwards. Beyond, there are only small round elevations and a single 

 row of large papillae similar to the preceding, in a 'line with the upper molars. In the 

 Sheep the mucous membrane is sometimes spotted black. 



3. Palate. In the Ox, the palate is most extensive. Its posterior third is quite 

 smooth, and the transverse ridges (bars) only occupy the anterior two-thirds. (They are 

 usually sixteen in number.) They are not curved, but are cut into notches on their 

 summit, which is inclined backwards. In the Sheep and Goat, as also in the Ox, is 



