THE HEART. 673 



right ventricle, part of them also entering the vortex, and "part, in the 

 anterior longitudinal sulcus, joining the middle muscular layers of the 

 left ventricle. Independent, superficial fibres occur only : 1, at the 

 conus arteriosus, arising from the ostium venosum dextrum, between the 

 right auricle and the aorta, surrounding the conus arteriosus, and re- 

 turning thence, from the left, back to their point of origin ; 2, at the 

 apex of the right ventricle, where not unfrequently a distinct, second 

 vortex exists, in which case some of the superficial fibres arising from 

 the left ostium venosum also curve inwards in that vortex, as they do in 

 that of the left ventricle, and are continued into the superficial fibres of 

 the right ventricle, but, on account of their intricate interlacement, 

 cannot be traced further. Besides these, other deeper fibres exist in the 

 right ventricle, which are disposed as follows: 1. From the upper bor- 

 der of the septum, and the left posterior side of the pulmonary opening, 

 flattened bundles commence and run in the septum, downwards and for- 

 wards, towards the apex of the heart and the anterior longitudinal sul- 

 cus, where they join the superficial fibres, and are continued with them 

 into the vortex, whence they may be traced as far as the anterior papil- 

 lary muscle of the left ventricle (Fig. 276 b, b', b"). 2. With these fibres 

 are associated others, running obliquely downwards and backwards, 

 from the right side of the pulmonary opening and the right portion of 

 the ostium venosum dextrum, beneath the superficial layer of fibres on 

 the free wall of the ventricle, as far as the posterior longitudinal sulcus, 

 where they curve abruptly towards the septum, in which they accom- 

 pany the fibres described under (1), though more on the inferior half of 

 the septum, to the apex of the^ heart, and terminate in a similar way. 3. 

 With these fibres are also conjoined, to some extent, the elements of 

 the great papillary muscle of the right ventricle, whilst those of the two 

 smaller are continued into the fibres of the septum described under (1). 

 Besides this, all these muscles furnish direct fibres, some of which de- 

 scend from the ostium venosum and return upon themselves, and some 

 proceed from the network of the trabeculai carnea? and cannot be traced 

 further. 



It would appear therefore, that the auricles, as regards their muscular 

 structure, are almost distinct; whilst in the ventricles, the entire super- 

 ficial, tolerably thick muscular layer is continuous all round and is dis- 

 posed as if the heart had only a single cavity. Properly speaking, the 

 left ventricle alone in this respect, is independent, in which there is not 

 only beneath the superficial layer a very thick muscular mass arising 

 and ending in it, to which, also, the greater part of the septum belongs, 

 but which also receives nearly all the deeper muscular layers arising on 

 the right side, in the free wall of the ventricle, and inserted into the 

 right portion of the septum. The heart, consequently, might be de- 

 scribed as composed of two muscular sacs; the thinner of which is com- 



43 



