THE RIGHT VENTRICLE 



531 



The axis of the cavity, taken from this ridge to the apex forms a spiral curve down- 

 ward and to the right. The septal wall is convex and faces obliquely forward 

 and to the right. 



The right atrio-ventricular orifice (Ostium v(>no.s\nn dextrum) is oval and is 

 situated opposite to the lower parts of the third and fourth ribs. It is guarded by 

 a tricuspid valve (^'alvula tricuspidalis) ; of the three large cusps of this valve, one 

 is l)etween tlie atrio-ventricular opening and the conus arteriosus, one is septal, 

 antl the third is on the right margin. Small intei'mediate cusps intervene between 

 the large ones. The peripheral edges of the cusps are attached to the fibrous ring 

 at the atrio-ventricular opening. The central edges are irregular and hang down 



A nterior vena 



Muscidus 



pectbiutus 



Bight coronary ■ - - 

 artery 



Tricuspid-' 

 valve ' 



CJiordxe- - 

 tendinecc 



Moderator, 

 band 



Right V 



Pulmonary 



Right coronary artery - 



Great coronar;/ 



vein 

 Left coronary 

 ^~— ^_ artery {airoum- 

 ' -^.^ flex branch) 



Bicuspid valve 

 Chord w tendinecc 



-Musculus papillaris 

 Moderator band 

 Left ventricle 



Fig. 423.— Sectio 



a OF Horse. 



Specimen hardened in situ and cut nearly at right angles to the ventricular septum. The left ventricle is contracted, 

 but not ad maximum. V. a., Segment of aortic valve. 



into the ventricle; they give attachment to chordae tendinese. The auricular 

 surfaces are smooth. The ventricular surfaces are rough and furnish attachment 

 to interlacing })ranches of the chorda? tendinese. The valves are folds of the endo- 

 cardium, strengthened by fibrous tissue and at the periphery by muscular fillers 

 also. The chordae tendinese are attached below to the three musculi papillares, 

 which project from the ventricular wall; superiorly they divide into l)ranches 

 which are insej'ted into the ventricular surfaces and the free edges of the valves. 

 Each segment of the valve receives chordae tendinese from two papillary muscles. 

 Of the latter, two are on the septum and the third and largest springs from the 

 anterior wall. 



The pulmonary orifice (Ostium arteriaj pulmonalis) is circular and is situated 



