162 



THE ARTICULATIONS OF THE TRUNK AND HEAD. 



upwards in inspiration, forwards and downwards in expiration. The last two ribs, forming 

 no costo-transverse articulations, move freely backwards and forwards, while the up and 

 down movement is more limited : the twelfth rib in inspiration is drawn backwards and 

 rather downwards. When the vertebral column is extended, the ribs are raised and separated ; 

 and when the column is bent forwards, the ribs are depressed and brought together. The 

 combined movements of I the chest- walls in respiration will be considered with the actions of 

 the thoracic muscles. 



TEMPORO-MAXILLABY ARTICULATION. 



The articular surfaces of this joint are the condyle of the lower jaw, which is 

 approximately a portion of a cylindrical tody, with its axis directed from without 



Fig. 189. A PORTION OP THE &KULL WITH THE 

 LOWER JAW AND HYOID BONE, SEEN FROM 



THE OUTER SIDE. (Allen Thomson, after 

 Arnold.) J 



1, external lateral ligament of the temporo- 

 maxillary articulation ; 2, a part of the capsule 

 of the joint ; 3, styloid process ; 4, stylo-maxil- 

 lary ligament ; 5, stylo-hyoid ligament ; 6, lesser 

 cornu of the hyoid bone with some short liga- 

 mentous fibres attaching it to, 7, the body, and 

 8, the great cornu. 



inwards and slightly backwards, and 

 the surface of the squamous portion 

 of the temporal bone extending over 

 the part of the glenoid fossa in front 

 of the Glaserian fissure and the articular 

 eminence formed by the anterior root 

 of the zygoma. The two are markedly 

 incongruent, and the temporal surface is much larger than that of the inferior 

 maxilla. The incongruence is compensated by the interposition of a meniscus 



Fig. 190. A PORTION OF THE SKULL AND LOWER JAW 

 WITH HALF THE HYOID BONE, SEEN FROM THE INSIDE. 



(Allen Thomson. ) 



The numbers are the same as in fig. 189 ; 3, styloid 

 process, detached from the skull ; 7, posterior surface of the 

 right half of the body of the hyoid bone ; 9, internal 

 lateral ligament of the temporo-maxillary joint ; 10, infe- 

 rior dental foramen. 



which divides the joint into an upper and a 

 lower synovial cavity. The layer clothing the 

 articular surfaces of the bones is composed of 

 fibro-cartilage. 



The external lateral ligament is a short 

 fasciculus of fibres, attached above to the lower 

 border and the tubercle of the zygoma ; and 

 below to the external surface and posterior 

 border of the neck of the lower jaw, its fibres 



being directed downwards and backwards. Scattered ligamentous fibres cover the 



synovial membrane in front, on the inside, and behind, forming a thin and loose 



capsule round the joint. 



The internal lateral ligament is a flat, thin band, placed at some distance 



from the joint. It extends from the spinous process of the sphenoid bone down- 



