512 CORONARY VESSELS. 



fibres is most complicated. They are first superficially placed, 

 and as they make their spiral turns, sink deep into the sub- 

 stance of the heart, somewhat like the contours of a leaf of 

 paper rolled into the form of a cone. They consist of fibres 

 proper to each ventricle, and fibres common to both. The 

 former, after arising from the zone, turn spirally around the 

 axis of the ventricle, so as to form many times the figure of 8, 

 and coming upon the anterior face of the same side, terminate 

 upon the zone surrounding the arterial orifice. The fibres 

 common to the ventricles are of two kinds superficial and 

 deep-seated. The superficial are divided into anterior and 

 posterior. The anterior arising from the anterior part of the arte- 

 rial and auricular zones, run obliquely downwards and to the 

 left, converging towards the apex of the heart ; these are rolled 

 around the axis of the left ventricle, and dip inwards to termi- 

 nate in, or form the columnae carnese. The superficial part of 

 this order of fibres, is common to both ventricles ; the deep- 

 seated part belongs to the left only. The posterior superficial 

 fibres arise behind from the auricular zones only, and run 

 downwards, so as to embrace the right border of the heart, 

 come in front of the heart and opposite to the septum ventri- 

 culorum, dip under the anterior superficial fibres, wind round 

 the axis of the right ventricle and terminate in its columnae 

 carnese. These also in part only, are common to both ven 

 tricles. 



The deep-seated fibres form the internal part of the walls of 

 the right ventricle. They arise from the fibrous zones of the 

 right side. The anterior portion of these fibres runs obliquely 

 downwards, and backwards to the septum ; the posterior and 

 internal, pass at once into the septum, roll themselves round the 

 left ventricle and are lost amidst the other fibres. Thus it 

 appears, that by removing the superficial layer of the common 

 stratum, the heart may be divided into lateral halves, each con- 

 sisting of two muscular sacs, an auricle and ventricle, adjoined 

 to those of the opposite side in the middle line. 



The external surface of the heart is covered by that portion 

 of the pericardium which adheres to it. Adipose matter is often 



