438 RELATIONS OF THE MOUTH WITH THE HEAD. 



various muscles attached to it and the head, is in its power, 

 strength, beauty and mechanical contrivance, incomparably 

 superior to any thing in human mechanics. The teeth have 

 not only a direct connection with the jaws, but by means of 

 their blood-vessels and nerves, they have nearly as direct 

 and close a relation with the brain and its membranes, the 

 eye, the ear, and the nose. The fifth pair of nerves come 

 from the brain and send branches to the teeth, jaws, eyes, 

 nose, ears, &c., endowing the whole with sensibility to pain, 

 and so close is this sympathy manifested between the teeth 

 and brain, that the simple act of teething frequently occa- 

 sions the most frightful convulsions ; while cases are not 

 wanting to show that irritation of this same set of nerves, 

 from decayed teeth, has been the cause of tic-douloureux, ul- 

 ceration of the eye, photophobia, blindness, and the most 

 excruciating pain of the ear. The internal maxillary artery 

 is the principal vessel establishing the vascular relationship 

 between the mouth and brain, and other parts of the head 

 and face. 



In congestion, apoplexy, and delirium, the condition of 

 the circulation in the brain is reported by an almost similar 

 state of the circulation in the mouth. The gums, tongue, 

 palate, tonsils, &c., by the same kind of anatomical rela- 

 tionship of blood-vessels and nerves, display each their 

 several sympathies with the other portions of the head. 



We now pass to the second division, the physiological rela- 

 tions of the mouth with the different parts of the head. 



The functions of the mouth have been stated to be those 

 of prehension, mastication, insalivation, suction, deglutition, 

 and speech ; functions lying at the very foundations of life 

 and connecting man with the outer world. 



The first series of these functions comprises the commen- 

 cing stages of digestion, which comprehend the preparatory 

 but essential elements in that grand and fundamental pro- 

 cess of nutrition, which not only builds up the head in all 

 its different parts, and supplies its daily and unceasing 

 waste, but further preserves, with an ever vigilant and un- 

 tiring care, all its various relations with the mouth, and 



