THE LOWER JAW. 1^5 



treatment ; or a few mashes, and gentle alteratives, will relieve the animal. 

 A few slight cuts across the bars with a lancet or penknife, and takini^ 

 care to avoid the principal artery and vein of the palate, the situation of 

 which has been just pointed out, will relieve the inflammation, and cause the 

 swelling* to subside ; indeed, this scarification of the bars will seldom do 

 harm, although it is far from being so necessary as is supposed. To the 

 brutal custom of the farrier, who sears and burns down the bars with a 

 red hot iron, we do most peremptorily object. It is torturing the horse 

 to no purpose ; and it is rendering that part callous, on the delicate sensi- 

 bility of which all the pleasure and safety of riding and driving depend. It 

 may be prudent in case of lampas to examine the grinders, and more par- 

 ticularly the tushes, to see whether either of them is endeavouring to make 

 its way through the gum. If with the gum lancet, or penknife, two incisions 

 across" each other be made on the tooth, the horse will experience im.mediate 

 relief. 



THE LOWER JAW. 



The posterior or lower jaw may be considered as forming the floor of the 

 mouth, {a, p. 63, or w, p. 68.) The body or lower part of it contains the 

 under cutting teeth, and the tushes ; the sides are two flat pieces of bone, 

 containing the grinders. On the inside, and opposite to a, p. 63, is a hole 

 through which blood-vessels and nerves enter to supply the teeth, and 

 some of which escape again at another hole on the outside, and near the 

 nippers. The branches are broader and thinner, rounded at the angle of 

 the jaw, and terminating in two processes. One, the coracoid, from its 

 sharpness or supposed resemblance to a beak, passes under the zygomatic 

 arch, (see p. 63,) and the temporal muscle, arising from the whole surface 

 of the parietal bone (see p. 70), is inserted into it, and wrapped round it; 

 and by its action, principally, the jaw is moved, and the food is ground. 

 The other, the condyloid, or rounded process, is received into the glenoid 

 (shallow) cavity of the temporal bone, at the base of the zygomatic arch, 

 and forms the joint on which the lower jaw moves. This joint is easily 

 seen in the cut at page 63 ; and being placed so near to the insertion of 

 the muscle, or the centre of motion, the temporal muscle must act with 

 very considerable mechanical disadvantage, and must possess immense 

 power. 



This joint is admirably contrived for the purpose which the animal re- 

 quires. It will admit freely and perfectly of the simple motion of a hinge, 

 and that is the motion of the jaw in nipping the herbage and seizing tlie 

 corn. But the grass, and more particularly the corn, must be crushed 

 and bruised before it is fit for digestion. Simple champing, which is the 

 motion of the human lower jaw, and that of most beasts of prey, would 

 very imperfectly break down the corn. It must be put into a mill; it 

 must be actually ground. 



It is put into a mill, and as perfect a mill as imagination can conceive. 



The following cuts represent the glenoid cavity in a carnivorous, or flesh- 

 eating, and herbivorous, or grass-eating animal, viz. the tiger and the 

 horse : the one requiring a simple hinge-like motion of the lower jaw 

 to tear and crush the food; the other a lateral or grinding motion 

 to bring it into a pulpy form. First examine this cavity in the tiger, 

 represented at B. At the root of the zygomatic process D, is a 

 hollow with a ridge along the greater part of the upper and inner side of 

 it, standing to a considerable height, and curling over the cavity. At the 



