622 



FIBRES OF THE HEART. 



same time presented. The other, describing 

 the formation, or winding up of the fibres, 

 comprehends the retracing of the fibres from 

 the centre to the circumference, showing their 

 respective origins, associations, courses, con- 

 nexions, and terminations, also the manner in 

 which they are wound up to form the two ven- 

 tricles into one compact conical body. 



The dissection. The first stage consists in 

 separating the superficial fibres from the two 

 ventricles, which, perhaps, cannot be accom- 

 plished in a more simple manner than by rais- 

 ing them in the forms of two wings and a tail, 

 as represented in Jig. 279, which is to be done 

 by commencing at the anterior coronary track, 

 cutting through the superficial fibres and de- 

 taching them by means of a blunt scalpel in 

 their natural direction, so far as their insertions 

 at the base ; this will be found to divest the 

 right ventricle, and, from their obliquity, a part 

 of the left. (See the left wing, CACC.) Then 

 recommencing at the anterior coronary track, 

 the fibres should be separated in the contrary 

 direction, over the left ventricle towards the 

 apex. These fibres take a very spiral course, 

 and as they approach the apex converge, but 

 on reaching it they twist sharply round upon 

 themselves, like the fibres of a thick cord, and 

 entering at the apex become the internal fibres 

 of this chamber. The remaining part of the 

 superficial fibres, extending from the apex to 

 the base, pertains exclusively to the left ventri- 

 cle; these should be divided an inch or two 

 above the apex, and the apicial portion detach- 

 ed, which will complete the tail, CRC. Its 

 fibres are represented, as they appear after sepa- 

 ration, untwisted. The basial portion of these 

 fibres should now be detached so far as the 

 annulus arteriosus, and reflected like the right 

 wing, CRC. These, as do most other fibres 

 which approach the base, take a more longitu- 

 dinal course, and in general they become so 

 separated as they diverge to encompass the 

 basial part of the heart, that they cannot be 

 raised in an entire layer unless some of the 

 subjacent fibres be taken with them. 



The second stage of the dissection comprises 

 the disconnecting the bands which compose the 

 outer or proper wall of the right ventricle. 

 The superficial layer of fibres having been re- 

 moved, there remain two other layers pertain- 

 ing to this wall of the ventricle, viz. the middle 

 and the internal. The middle is separable into 

 two bands, the upper or basial, and the lower 

 or apicial. It is better to detach the apicial 

 band first, which makes one spiral circle round 

 the heart. Its outer extremity being attached 

 to the root of the aorta at its anterior face, and 

 sometimes to the pulmonary artery also, an in- 

 cision should be made extending from the up- 

 per part of the anterior coronary track obliquely 

 towards the annulus arteriosus, which incision 

 should, in a calf's heart, be a little more than 

 an inch in length and a tenth of an inch in 

 depth. The band should then be detached 

 agreeably to its spiral course from the base and 

 middle third of the left, and from the lower half 

 of the right ventricle, as far as the anterior co- 

 ronary track, the line from which the separation 



commenced. It here receives on its posterior 

 surface a considerable accession of fibres from 

 the right surface of the septum, by the junction 

 of which this part of the boundary of the ven- 

 tricle is formed, but the further separation of 

 the band prevented, \v\fig. 281, in the first or 

 basial part of its course it is indistinctly seen, 

 marked CACC. In. fig. 282 its middle course 

 may be traced, although the half circle of the 

 band which wound round the left ventricle has 

 been cut off. In the preparation exhibited in 

 this figure the separation of this band could not 

 be effected under the posterior coronary track, 

 on account of the separation having been con- 

 ducted too deeply, where the fibres decussate 

 to form the posterior boundary of the right ven- 

 tricle. In Jig. 281, which exhibits a dissection 

 of the right ventricle of a bullock's heart, the 

 whole of the band, CACC, is separated as far 

 as the anterior boundary of this cavity, and lies 

 extended; and the accession of fibres it re- 

 ceives from the right surface of the septum are 

 seen prolonged into it. 



The basial band crosses the upper half of 

 this ventricle. It cannot be raised from its 

 situation on account of the numerous lateral 

 connexions it forms in its progress with the 

 margins of the orifices of the aorta, pulmonary 

 artery, and annulus venosus. In order to de- 

 tach it as far as it will admit, an incision about 

 half an inch on the right side of and parallel 

 with the anterior coronary track, should be 

 made, extending from its lower edge to the 

 base, and an eighth of an inch in depth, or as 

 deep as will expose the fibres from the pulmo- 

 nary arteiy, which in general pass at an angle 

 with those of the band. Although this band 

 cannot be disconnected from the base, it can in 

 general be detached from the fibres of the sub- 

 jacent layer, so far as the posterior coronary 

 track ; sometimes, however, they are too inter- 

 woven to admit of any separation. The first 

 part of this band is represented in Jig. 281, 

 marked CPCAA; it was divided more than 

 half an inch from the anterior coronary track. 

 Its continuation may be seen in ^.282, lettered 

 CPCAAA, where it is evidently not discon- 

 nected from, but merely raised towards 

 the base, and if replaced would overlap the 

 fibres taking the middle course round the heart. 

 The depression at the line of the posterior coro- 

 nary track, pet, is occasioned by the band being 

 bound down at the base and at its under sur- 

 face also, by which means the upper half of the 

 posterior boundary of this ventricle is formed. 

 As the further pursuit of this band pertains to 

 the third stage, it will be made hereafter. 



The internal layer. By the separation of 

 the two former bands the internal layer is ex- 

 posed. It is composed of fibres from the pul- 

 monary artery and from one of the carnea co- 

 lumnse. In Jig. 281 the fibres, PC, are seen, 

 arising from the root of the pulmonary artery at 

 its entire circumference, first forming a channel 

 and then expanding into a layer, which, in pro- 

 ceeding obliquely across the cavity, obtains an 

 accession of fibres from one of the carneoe co- 

 lumnae, which is not brought into view, and 

 which, on reaching the line of the posterior 



