FIBRES OF THE HEART. 



623 



coronary track, joins a band emerging from the 

 septum, and thus forms the apicial half of the 

 posterior boundary of this ventricle. It is 

 raised from its situation, but when replaced us 

 edge, which is everted by the probe, applies 

 itself to the anterior boundary of this cavity. 

 This layer cannot often be so extensively dis- 

 connected from its superjacent bands as this 

 figure represents. 



The third stage of the dissection. Having 

 separated the layers composing the right or 

 proper wall of the right ventricle, the next pro- 

 ceeding consists in detaching and unwinding 

 the band and layers composing the left ventri- 

 cle. First, the detachment of the basial band. 

 As this band has already been detached over 

 the right ventricle in the second stage of the 

 dissection, it is necessary to resume its separa- 

 tion at the posterior coronary track. But as 

 the further separation is somewhat difficult, it 

 will be rendered less so if the remaining portion 

 of this band be first examined in Jig. 282, 

 wherein it is represented detached. When in 

 its natural situation it forms the uppermost 

 third of this, the left ventricle, and its lower 

 fibres overlap a part of those which occupy the 

 middle third. The fibres which overlap the 

 others in taking an oblique course towards the 

 base reach the brim of the ventricle and pass 

 over it, while the under fibres of this band are 

 appearing in succession, and taking a similar 

 spiral course until the whole bundle of fibres is 

 twisted in the form of a rope. In order, there- 

 forego trace out and detach this band as it becomes 

 transformed into a rope, it is requisite to com- 

 mence near the posterior coronary track (pet), 

 in a continuous line with the lower edge of its 

 former portion, introducing the handle of a 

 scalpel obliquely upwards so as to detach the 

 fibres which overlap those of the middle third, 

 and to carry the separation so far up as will 

 reach those marked A, coming obliquely down 

 from the aorta. In conducting this separation 

 from left to right it is soon found that the fibres 

 of this bundle, instead of overlapping others, 

 become themselves by twisting overlapped, 

 rendering it necessary, therefore, to turn gra- 

 dually the handle of the scalpel obliquely 

 downwards, tracing the rope according to its 

 windings. Two scalpels will be required in 

 conducting the further separation. 



The next step should be preceded by viewing 

 the fibres of the rope in fig. 280, descending 

 and radiating into a layer which sweeps round 

 the cavity of this ventricle. The heart should 

 now be placed in a small cup or jar of a size 

 that will support it with its base upwards, and 

 then, with the scalpels employed vertically, the 

 separation should be proceeded with, and in 

 passing through the septum a vertical section 

 shouloT be made through the aorta in the 

 line of separation, which should be pursued 

 round and round, and progressively deeper 

 until the handles of the scalpels perforate the 

 external fibres, which, if they have been rightly 

 inclined, they will do a little above the apex of 

 the left ventricle, just after they have completed 

 the division through the layers of the septum. 

 The band of fibres occupying the middle third 



of the heart, and which now pass over the scal- 

 pels, should be divided ; the incision being 

 made along the side of the posterior edge of 

 thr xcptuin. A section should be made through 

 the rope also, which allows the right ventricle 

 to be raised from the left, and the heart to be 

 unwound as far as the separation has been car- 

 ried. There yet remains a mass of fibres 

 around the cavity of the left ventricle to be de- 

 tached. This last process of separation should 

 be conducted in a contrary direction to that 

 which has hitherto been adopted, viz. from right 

 to left, until the internal membranous lining is 

 exposed, and which should be torn in order to 

 lay open this chamber. 



The heart can now be unwound and extended 

 as mfig. 278, placing the left ventricle, hi, at 

 one end and the right at the other, removing 

 that section of the aorta, AA, connected to the 

 right ventricle from its counterpart which ex- 

 clusively pertains to the left, and which is hid- 

 den by the rope, RR ; removing also the two 

 portions of the bisected rope to the two most 

 distant diagonal points in this view. The 

 niche, CPC, indicates the part occupied by 

 the divided band which passed along the mid- 

 dle third of the heart. 



The second method of demonstration. The 

 formation, or winding up of the fibres, 

 of the heart. This description comprehends 

 the retracing of the fibres from the centre to 

 the circumference, showing their respective 

 origins, associations, courses, connexions, and 

 terminations, also the manner in which they 

 are wound up to form the two ventricles into 

 one compact conical body. 



The jirst stage consists in retracing the su- 

 perficial layer from its origins to its termina- 

 tions. It is necessary to commence at the 

 very centre of the heart the interior of the left 

 ventricle, whence spring the fibres composing 

 its main bulk. Fig. 278, at its right extremity, 

 exhibits the left ventricle, lv, laid open, exposing 

 the two carneae columnae, cc and cc, one of 

 which is placed out of its situation, in order to 

 show the interior of the chamber. The fibres 

 of the two carneae columnar, cc and cc, ex- 

 pand in a fan-like manner ; those of the rope, 

 nil, expand in a similar manner ; the radiated 

 fibres of each of these three bodies wind round 

 the axis of this ventricle forming its parietes ; 

 and as they wind so as to form an inverted 

 cone, it is clear that the inmost fibres alone 

 can reach the apex. Accordingly, a fasciculus 

 of the inmost fibres from each of these three 

 bodies, marked c, n, and c respectively, pass 

 down to the apex associated together, and in 

 their course make a gentle twist from left to 

 right, gradually contracting the cavity to a 

 point and closing it; they then twist sharply 

 round upon each other and complete the apex 

 marked CRC conjointly, so that by means of 

 this twisting the internal fibres are rendered 

 external. These excluded fibres now enter into 

 the formation of the superficial layer, and form 

 the tail of Jig. 279. They take a very spiral 

 course near the apicial part, and over the an- 

 terior surface of the left ventricle as far as the 

 anterior coronary track ; but as they approach 



