TEMPORO-MAXILLARY ARTICULATION. 



937 



condition of the frame. These peculiarities 

 react to a certain extent upon the mind, and 

 more or less aid or clog its workings, but cer- 

 tain powers and modes of action of the mind 

 are by no means so constantly associated with 

 certain states of body, as to connect the men- 

 tal and bodily states as cause and effect. It 

 is true that the sanguine temperament is ge- 

 nerally accompanied by a mind exhibiting 

 certain characters, but the exceptions to this 

 are so numerous that we cannot assign the 

 corporeal state as the cause of the mental 

 nor vice versa. Bodily peculiarities are in- 

 finitely more frequently inherited than mental, 

 the powers and activity of the mind are 

 greatly determined by education and training; 

 but those qualities of body which give a cha- 

 racter to its temperament are born with it ; 

 and although they may be modified by exter- 

 nal influences, they are yet at all times suf- 

 ficiently distinct to prove them to be inherent 

 physical properties of the entire organism. 



At the same time it seems reasonable to 

 admit that the mind has its temperaments, as 

 the body has, and in a great measure inde- 

 pendently, and the terms, sanguine, melan- 

 cholic, phlegmatic, and choleric, may be 

 severally applied to them, according as the 

 emotions and feelings, and the intellectual 

 actions vary in their modes and degrees of 

 developement, and in their rate of working. 



(R. B. Todd.) 



TEMPORO-MAXILLARY ARTICU- 

 LATION. Under this heading I propose to 

 give a brief account of the jointing of the 

 lower maxilla to the cranium. This joint can- 

 not, of course, be identified out of the verte- 

 brata. The mandibles and maxillae of the ar- 

 ticiilnta are not homologous with the jaws of 

 vertebrate animals, and the slit of their mouths 

 is placed vertically not horizontally. 



In the human subject, as in all mammalia, this 

 articulation takes place between the squamous 

 portion of the temporal (squamosal) and the 

 inferior maxillary bones. The description of 

 the anatomy of the human temporo-maxillary 

 joint comprises, therefore, that of the diarthro- 

 dial articular surfaces of those bones, and also 

 of the following parts : viz., the interarticuiar 

 fibro-cartilage, the two synovial sacs, the ex- 

 ternal and internal lateral and other liga- 

 ments, and part of the insertion of the external 

 pterygoid muscle. 



Hones. The articular condyle of the lower 

 jaw is sub-cylindroid in form, its length from 

 side to side being greater than its antero-pos- 

 terior measurement. The axis of this c} limler, 

 however, is set neither directly from side to 

 side, nor yet exactly level, its inner part being 

 posterior to and below its outer; so that if 

 the axes of the two condyles were produced 

 inwards till they met, they would form an 

 angle in doing so, which would point down- 

 wards and backwards, reaching the anterior 

 margin of the foramen magnum. The carti- 

 lage that encrusts this condyle extends further 

 down behind than in front. 



The surface to which this condyle is 



(mediately) articulated forms a part of the 

 glcnoid fossa, and is situated just below the 

 base of the zygomatic process of the temporal 

 bone, between its roots. It has such form 

 as, in respect of the set of its axis, and its 

 tranverse measurement, pretty accurately fits 

 the condyle. It has, however, a greater 

 antero-posterior extent, in accordance with 

 the capability which this joint normally pos- 

 sesses, in addition to the usual ginglymoid 

 motion, of an antero-posterior gliding to and 

 fro of the condyle a kind of normal disloca- 

 tion. The glenoid fossa of the temporal bone 

 contains a portion of the parotid gland, as 

 well as the condyle of the inferior maxilla ; the 

 former occupies that portion of it which is 

 posterior to the glasserian fissure, whilst that 

 part which is anterior to the glasserian fissure, 

 is lined with cartilage for the articulation of 

 the latter. In man there is usually no bony 

 ridge bounding this articular surface pos- 

 teriorly, such as is generally found in the 

 lower mammalia. 



The ridge that bounds it anteriorly is formed 

 by the inferior root of the zygoma, and the 

 cartilage is continued some way on to this 

 ridge. Externally it is limited by a tubercle 

 on the zygoma, which serves for the attach- 

 ment of the external lateral ligament of the 

 joint. 



Interarticuiar fibro-cartilage. This is a 

 thin disc or meniscus, oval or sub-oblong in 

 form, concave below and convex above, thus 

 capping the condyle, thicker at the edges than 

 in the middle, where it is not unfrequently 

 thinned away even to perforation. It differs 

 from all the other fihro-cartilages in having 

 muscular fibres inserted into it; namely, a 

 portion of those of the external pterygoid. 

 This insertion takes place along its anterior 

 border, and by it the fibro-cartilage is made to 

 join in that normal amount of dislocation for- 

 wards, which as above stated, the condyle of 

 the lower maxilla is capable of, as well as in 

 the abnormal accidental dislocation of the 

 jaw. It is further held in its place by the 

 fibres of the external lateral ligament, and by 

 the synovial bursae of the joint. 



Synovial Bursts, These are two in num- 

 ber, one above the interarticuiar fibro-carti- 

 lage and the other below it. The upper one 

 is the larger and slacker, for it alone is con- 

 cerned in the antero-posterior gliding of the 

 joint. The two sacs, of course, communicate 

 and are reduced to one when the interarti- 

 cuiar fibro-cartilage is perforated in the 

 centre. 



Ligaments. There is only one ligament in 

 immediate relation with the temporo-maxil- 

 lary joint, namely, the external lateral. This 

 is a small ligament, broader above than below, 

 situated at the outside of the joint; attached 

 above to the tubercle situated at the point 

 of divergence of the roots of the zygoma; and 

 directed downwards and backwards to the 

 outside of the neck that supports the condyle 

 of the lower jaw. Midway in its passage from 

 the one to the other it is attached by its inner 

 aspect to the interarticuiar fibro-cartilage. 



