260 



THE HEART. 



may eventually be traced at one end to the tendinous structures at the 

 base of the heart, and at the other to one of the papillary muscles of the 

 left ventricle. 



The peculiar spiral concentration of the fibres of the heart at the apes is 

 known as the vorfcv or irhorl. and is pi-oduced. as already described, by the 

 twisting or interlocking of the fibres in the interior as they pass to be con- 

 tinuous with those on the exterior. It has been thought that a similar continuity 

 was the rule at the base of the heart also, and that few if any of the bundles 

 are attached to the tendinous rings. But although it is true that some bmidles 

 may tui-n round at the auriculo-ventricular openings, this is by no means general, 

 and most of the miiscidar fasciculi must be described as being attached to the 

 fibrous and fibro-cartilaginous structures at the base, either directly or through 

 the medium of the chordas tendineaa and segments of the valves. 



Fi>. 17S. 



Fig. 178. — View op the Fibkes of 

 THE Sheep's Heakt, dissected at 

 THE Apex to show the " voktex " 

 (Pettigrew). 



«, a, fibres entering the apex 

 posteriorly at h ; c, c, fibres entering 

 the apex anteriorly at d. 



In the middle of the thickness of 

 the ventricular wall the fibres are, 

 as before said, annular and trans- 

 verse (fig. 179, 4, 4') ; but, as 

 Ludwig showed, they pass by the 

 most gradual transition into the 

 diagonal ones nearer the surfaces, so that any separation into layers which 

 may be effected (with the exception of the superficial stratum previously 

 described) must be looked upon as in a gi-eat degree artificial. Even by those 

 anatomists who contend for the existence of definite strata then' number has 

 been veiy differently stated. Wolff * conceived that five layers might be made 

 out. Pettigrew f has described as many as seven in the wall of each ven- 

 tricle, of which the fourth occupies the middle of the thickness of the ven- 

 tricular Avail ; the thii-d is continuous above and below •udth the fifth ; the second 

 ■with the sixth ; and the first, or most external, with the seventh, or most internal ; 

 the outer layers tui-ning in at the whorl and at the margins of the aui-iculo-ventri- 

 cular openings respectively, but without being attached to the tendinous struc- 

 tm-es at all. 



It wiU be observed that Pettigrew's description differs materially from that 

 given in the text, which, although agreeing in many points with the observations 

 of Ludwig, AVinckler, and Sibson.J is mainly fomrded on an entirely fresh inves- 

 tigation of the subject, undertaken with the co-operation of Mv. F. J. Davies, of 

 University College. 



Interstitial structures. — The interstices between the closely reti- 

 culating muscular fibres are filled by connective tissue, with nmnerous 

 blood-vessels, lymphatics, and nerves. The muscular substance is 

 supplied Avith -blood by the coronary arteries, the orio-in and course of 

 which, as Avell as of the coronary vein, are elsewhere described. The 

 smaller branches penetrate into every part of the muscular substance. 



The lymphatics (which are found in great number beneath both the 

 pericardium and endocardium), are also, according to Schweigger-Seidel, 



* C. F. Wolff, Do ordine Fibrarum Muscularium Cordis ; Act. Acad. Petropol. 1780 

 —1792. 



t Phil. Trans. 1864. 



X Liulwig, ill Zeitsclirift fur rationelle Medizin, 1849 ; and Milller's Archiv. Winckler, 

 in Archiv fiir Anatomie und Physiologic, 1865. Sibson, Medical Anatomy, 1SG9. 



