MUSCLES OF MASTICATION. 153 



may, in this point of view, be considered as a sort of fingers 

 fixed within the mouth, destined to feel, examine, and adjust 

 the morsel preparatory to placing it in the position most fa- 

 vorable to its mastication." * He further states that though 

 this subject has engaged his attention for several years, he 

 has observed no cases of paralysis in which this peculiar sen- 

 sibility was affected. 



In persons who use false teeth, the pressure on the gums 

 in mastication takes the place imperfectly of the tactile sen- 

 sibility of the natural teeth. The sensibility of the latter is 

 dependent, undoubtedly, on the nerves distributed to the 

 dental pulp. 



Summary of the Process of Mastication. The various 

 muscles attached to the lower jaw are competent to bring 

 the teeth together, and to produce a lateral movement and a 

 movement backward and forward. Some articles of food are 

 torn asunder by movements of the head and the upper ex- 

 tremities, as in the carnivora, or divided by the incisors, as 

 in the herbivora. After the food is taken into the mouth, it 

 is kept between the molars and subjected to their triturating 

 action, which is. effected by movements of opening and clos- 

 ing the jaws, conjoined with marked lateral movements. 

 The position of the muscles and the peculiar construction of 

 the temporo-maxillary articulation are sucli as to enable the 

 condyles of the inferior maxilla, on either side, to alternately 

 slide forward, producing rotation and deviation of the bone 

 to the opposite side. In this movement, the condyle, cov- 

 ered by the pliable inter-articular fibro-cartilaginous disk, and 

 thus presenting a concave articulating surface, is brought in 

 contact with the articulating eminence in front of the gle- 

 noid cavity of the temporal bone. 



Mastication should be continued until the alimentary bolus 

 has become thoroughly triturated. . The food, at the same time, 



1 GRATES, On a Peculiar Affection of the Nerves of the Teeth. Dublin Jour- 

 nal of Medical Science, 1836, vol. ix., p. 3. 



