934 



THE ORGAXS OF CIRCVLATION 



The auriculo- ventricular opening is unaixUd by the bicuspid valve. Its two 

 une<iual se<rinents are larirer and thicker than those on the rij^ht side of the lieart, 

 thousjh the^oriliee itself is somewhat smaller, and they are similarly separated by 

 smaller lobes or cusps. Of the two segments, the one, which is the larger and the 

 more free and smooth, is i)laced in front and to the right l)etAveen the two open- 

 int^s, whilst the other lies behind and to tlie left. The fibrous ring surrounding the 

 orifice serves to give attachment to muscular fibres as Avrll as to the valves. By its 

 right border it is tied to tlie aortic ring by fibrous tissue, which also extends to the 



Fig. 553.— Postbrior View of the Left Chambers of the Heart, with the Great 

 Vessels and the Coronary Sinus laid open. 



Left carol ill 



Left mhclmian 



LEFT AURICULAR APPENDIX 



INTERIOR OF LEFT AURICLE - 



Great cardiac rein 



Vulres of great canliac 

 vein 



ANTERIOR 

 SEGMENT OF 

 MITRAL VALVE 



Innontinate 



Ductus urtf-rioius 



Commencement of left 

 pulmonary 



Left jiulnionari/ reins 



CONCAVE EDGE OF THE VALVE 

 OF THE FORAMEN OVALE 



Rifjlil ptilmonai-y 



reins 

 Left auriculu-rentri- 



culiir open in </ 

 Valved orifice of rein 



in coronary sinus 

 Coronary sinus 



Valve if T/iebesius 

 I en« lara inferior 



POSTERIOR SEGMENT OF MITRAL 

 VALVE 



CHORD/E TENDINE/E 



Compound posterior papil- 

 lary muscles 



FINE MESH- 

 WORK OF 

 COLUMN/t 

 CARNE/E 

 AT APEX OF 

 VENTRICLE 



Coronary artery 



SECTION THROUGH VALL OF LEFT 

 VENTRICLE 



COLUMN/E CARNE/E 



ring surroun(Hng tlic tricus])id valve. In the angular space thus bound(Ml there is 

 imljedded a fibro-cartilagc, whicli in somcMuammals is represent(Hl by a l^oiie wliich 

 is known as the os cordis. 



The interventricular .^eptum whicli separates the cavities of the ventricles is 

 thickest beloAV. In the greater part of its extent it consists of muscular tissue, but 

 its upper portion, which intervenes not only betw^een the two ventncl(>s Init also 

 between the left ventricle and right auricle, is a fibrous septum devoid of nmscle- 

 fibres. 



