♦ 



134 THE ANATOMY OF THE HORSE. 



be effected by cutting the auriculo-ventricular fibrous rings, which 

 form the bond of connection between the auricular and ventricular 

 fibres. By combined cutting and teasing the following facts may be 

 observed. 



Over the whole exterior of the ventricles the fibres have an oblique 

 direction. Thus, on the left side the fibres pass obliquely downwards 

 and backwards, and on the right side downwards and forwards. At the 

 left ventricular furrow many of the fibres dip into the septum ; but on 

 the right side the fibres of the left ventricle pass across the furrow, and 

 are directly continued on the right ventricle. At the apex of the heart 



Fig. 14. 



View of a Partial Dissection of the Fibres of the left Wall of the Ventricles in a 

 Sheep's Heart designed to show the different Degrees of Obliquity of the Fibres. 

 (Allen Thomson.) 



At tlie base and apex the superficial layer* of fibres is displayed ; in the intervening space more 

 and more of the fibres have been removed from above downwards, reaching to a greater depth on 

 the left than on the right side. aX. a 1 . The superficial layer of the right ventricle, ; 6 1 . b\ The same 

 of the left ventricle ; at 2 this superficial layer has' been removed so as to expose the fibres under- 

 neath, which are seen to have the same direction as the superficial ones over the left ventricle, but 

 different over the right ; at 3 some of these have been removed, but the direction is only slightly 

 different ; 4. Transverse or annular fibres occupying the middle of the thickness of the ventricular 

 walls ; 5, 6, 7. Internal fibres passing downwards towards the apex to emerge at the whorl ; between 



c. c. the left ventricular groove, over which the fibres of the superficial layer are seen crossing ; in 

 the remaining part of the groove, some of the deeper fibres turn backwards towards the septum ; 



d. The pulmonary artery ; e. The aorta. 



the fibres turn inwards in a whorl-like manner and disappear from view. 

 If a thin stratum of these superficial fibres be now removed they will 

 be found to cover others having a less oblique course ; and further 

 dissection will show that the fibres become less and less oblique until 

 the centre of the wall is reached, where the fibres are approximately 

 horizontal. On peeling off these horizontal fibres a deeper set will be 

 exposed which are slightly inclined, but in a direction opposite to the 



