HEART. 



583 



anterior fissure from the apex near to the com- 

 mencement of the aorta, then another in- 

 cision midway between the posterior fissure 

 and left edge of the ventricle, commencing near 

 the base and carrying it downwards to join the 

 other at the apex. The anterior and right 

 parietes of the internal surface are formed by 

 the septum ; the posterior and left belong ex- 

 clusively to itself. The walls of the left ven- 

 tricle are considerably thicker than those of the 

 fight, and remain apart, while those of the right 

 fall together. As connected with this we may 

 observe that the septum is concave towards the 

 left ventricle and convex towards the right. As 

 the obstacles to be overcome in transmitting the 

 blood through the body are greater than those 

 to be overcome in transmitting it through the 

 lungs, so is the left ventricle thicker than the 

 right. It is important to remark, as connected 

 with the pathology of spontaneous rupture of 

 the heart, that the walls of the left, like those 

 of the right ventricle, are considerably thinner 

 at the apex than towards the base.* The ante- 

 rior and right parietes are longer than the pos- 

 terior and left. The columnae may be arranged 

 into three kinds, such as we have described in 

 the right ventricle. They are not so numerous 

 in the left ventricle as in the right. The greater 

 number are also smaller, and are principally 

 placed upon the posterior and left wall, near the 

 apex of which they form deep areolae.f The 

 upper part of the septum which leads to the 

 aortic opening, which we shall presently describe, 

 is quite smooth. In the base of the ventricle 

 we find two openings placed closely together ; 

 one of these, the smaller, is placed to the right 

 and a little anterior, is the commencement of 

 the aorta, and occupies the upper and right 

 corner of the ventricle ; the other is larger and 

 placed to the left and a little posterior, and is 

 the auriculo-ventricular opening of this side. 

 The aortic opening is only separated from the 

 auriculo-ventricular opening by the tendinous 

 ring, and from the orifice of the pulmonary 

 artery by the upper part of the septum. A 

 valve resembling the tricuspid is attached to 

 the tendinous ring around the auriculo-ventri- 

 cular opening, which, from being more de- 

 cidedly divided into two lips, is termed bicuspid, 

 and from its fanciful resemblance to a bishop's 

 mitre has generally received the name of mitral 

 valve. Like the tricuspid it forms a complete 

 ring around the margin of the auriculo-ventri- 

 cular opening. The anterior lip of the valve in 

 the quiescent state of the heart hangs suspended 

 between the auriculo-ventricular opening and 

 the origin of the aorta, and is considerably 

 larger and more moveable than the posterior, 

 which is smaller and more limited in its move- 



* The circular arrangement of the muscular 

 fibres around the apex (fig. 274) must have the 

 effect of rapidly approximating the inner surfaces 

 of the ventricles at the apex during their systole, 

 more particularly when the apex is elongated, as in 

 the heart of the horse, and thus prevent the pres- 

 sure from falling upon the extremity of the apex, 

 where it is very weakly protected. 



t Laennec has erroneously stated in general 

 terms that the columns of the right ventticlc are 

 larger than those of the left. 



ments. The mitral valve is formed in the same 

 manner as the tricuspid, and is somewhat 

 thicker and stronger, and like it contains a 

 number of tubercles in its free margin. The 

 large anterior lip of the mitral valve projecting 

 downwards into the ventricle was described by 

 Lieutaud and by others since his time as 

 dividing the ventricle into two portions, an 

 aortic and a ventricular. These are separated 

 from each other at the upper part by the valve 

 only; at every other part they communicate 

 with each other. The same authors have 

 described the larger lip of the tricuspid valve 

 as effecting a similar division of the pulmonic 

 ventricle. Two of the columnae carneae in the 

 left ventricle belong to the third kind (musculi 

 papillares) already described, and are much 

 stronger than any to be found in the right ven- 

 tricle. They are attached to the lower part of 

 its cavity, pass upwards, and about the middle 

 of the ventricle terminate in a blunt extremity, 

 from which a number of chordae tendineae pass 

 to be attached to the margins of the mitral 

 valve. Bouillaud describes these two columnae 

 as uniformly occupying the same position, one 

 being placed at the junction of its left and 

 posterior walls to form the left margin of the 

 heart ; the other on the posterior wall near its 

 junction with the posterior margin of the sep- 

 tum.* Each of these fleshy columns consists 

 of two fasciculi, of an anterior and superior, 

 and of a posterior and inferior. The posterior 

 and inferior fasciculus is shorter and less strong 

 than the anterior. The chordae tendineae of 

 the two anterior or internal fasciculi proceed to 

 attach themselves to the margins of the anterior 

 or larger lip of the valves, those from one 

 fasciculus passing to one edge of the lip, and 

 those of the other fasciculus to the other ed^e. 

 As these chordae tendineae proceed from the 

 fasciculi to the valve, they diverge from those of 

 the same fasciculus, but converge towards those 

 of the other fasciculus. (Fig. 269 shews the 

 attachment of the chordae tendineae of the two 

 anterior or internal fasciculi.) The chordae 

 tendineae from the posterior fasciculi pass in a 

 similar manner to be attached to the posterior 

 lip. The posterior lip is fixed closer in its 

 situation than the anterior, by the chordae ten- 

 dineae, and this is frequently increased by some 

 of these cords passing from the walls of the 

 ventricle to be attached to the ventricular sur- 

 face of the valve, sometimes nearly as high as 

 the fixed margin of the valve. These chordae 

 tendineae are stronger, fewer in number, and 

 less subdivided than those in the right ventricle. 

 Several of them pass between the fleshy columns 

 without being attached to the valves, as in the 

 right ventricle. Though the description here 

 given is not perfectly uniform in every case, but 

 is liable to frequent varieties, by the non-divi- 



* I have satisfied myself by numerous examina- 

 tions, of the accuracy of Bouillaud's account of the 

 position of these musculi papillares and the arrange- 

 ment of the chordae tendineae in the human heart. 

 I have found them occupying a similar position in 

 the heart of the horse, ox, ass, sheep, pig, dog, 

 rabbit, hedge-hog, and some birds, and suspect 

 that this will be found a general law in all th 

 warm-blooded animals. 



