142 THE AHTim.M l"\*. 



is confounded in front with that of tho opposite gido. Tho inferior 

 portion, tho inferior stellate or costo-stcrnal //<//////////, is in relation with tlio 

 pectoral muscles. 



Synodal capsule. There is one for each articulation. 



Characters proper to the first coxtit-xti-nril nrticulation. The first costo- 

 stornal articulation is not separated from its fellow of tho opposite side ; so 

 that these two joints are, in reality, only one, and the two cartilages lying 

 close to each other correspond by a small diarthrodial facet, continuous with 

 that for the sternum. Tho two sternal facets are inclined upwards, and 

 confounded with one another. Only one synovial cavity exists for this 

 complex articulation, which unites the two first ribs to each other and to the 

 sternum. 



3. Chrondo-costal Articulations uniting the Ribs to their Cartilages. 



Those are synarthrodial articulations whoso movements are very obscure. 

 They are formed by the implantation of tho cartilages in tho rugged cavities 

 the ribs present at their inferior extremities. The solidity of these articu- 

 lations is assured by the adherence of tho fibro-cartilago to the proper 

 substance of tho ribs, and by the periosteum which, in passing from the 

 bone to tho cartilage, plays the part of a powerful peripheral baud. 



In tho Of, the sternal ribs, in uniting with their cartilages, form a veritable 

 ginglyinoid diartlirosis, whose movement is facilitated by a small synovial capsule. 



4. Articulations of the Costal Cartilages with each other. 



The ribs, attached to each other by means of the intercostal muscles, are 

 not united by real articulations ; neither are their cartilages of prolonginont. 

 But the asternal cartilages are bound together by a small yellow elastic 

 ligament, which is carried from the free extremity of each to tho posterior 

 border of tho preceding cartilage ; the anterior border of the first asternal 

 cartilage is directly united to tho posterior border of the last sternal cartilage, 

 through the medium of the perichondrium and very short ligamentous bands. 

 This same asternal cartilage is also bound to the inferior face of tho xiphoid 

 appendage by a small white ligament (tho chondro-xiphoid), under which 

 passes the anterior abdominal artery. 



5. Sternal Articulation peculiar to tlie Ox and Pig. 



It has been already shown that in these animals tho anterior piece of the sternum is 

 not consolidated with the second portion. Tho two nre united by a diurtlimdial 

 articulation; and for this purpose the anterior presents a concave surface, tlie pdMrrior 

 a convex one. Bundles of peripheral fibres firmly bind them to each other, and a .sp.-eial 

 small syuovial capsule facilitates their movements, which are very limited. 



6. The Articulations of tlie TJiorax considered in a general manner in regard to 



Movements. 



Tho thorax can increase or diminish in diameter in an antero-postcrior 

 and a transverse direction; whence arises tho dilatation and conf ruction 

 of this cavity : tho inspiratory movements accompanying tho entrance of the 

 external air into tho lungs, and tho expiratory movement* expelling tho air 

 contained in these organs. 



The variations in the antero-posterior diameter of the chest Ix-ing due fo 

 changes in tho figure of tho diaphragm, need not bo noticed hero. P.nt Hie 

 transverse variations being tho result of tho play of tho costal arches on the 



