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unravel the intricacy of these fibres*. Fibres of the ordinary structure,' 

 and crossing each other, in various directions, form the two auricles; 

 other and more numerous fibres form the parietesof the ventricles, reach 

 from the apex to the base, extend into the septum which divides them, 



* On this point the author is by no means correct. The structure of the heart may 

 be demonstrated with tolerable accuracy. The latest and best description of it has been 

 furnished by J. F. VAUSS, teacher of anatomy in the University of Liege. 



As an accurate view of the distribution of its fibres is requisite to enable us to know 

 the nature of the actions of this viscus, the following account by this anatomist is here 

 introduced : 



" The heart is a conical hollow muscle, covered by the serous membrane, the peri- 

 cardium lined by a membrane, which is of a different, nature in each ventricle, and 

 composed of three layers of muscular fibres : the superficial one common to both ven- 

 triclesthe middle one at least four times as large as the preceding, and like it, com- 

 mon to the two great cavities of the heart and the lower one, divided into two parts, 

 the right and the left, each belonging to the corresponding ventricle ; both of them 

 forming the septum by their junction, and giving birth to the column carneae. 



" The other layer is very fine ; its bundles of fibres which become more oblique as 

 they get lower, are directed, the anterior ones from the right to the left, and the pos- 

 terior ones from left to right, from the base to the apex of the heart, where they are 

 confounded with the fibres of the middle layer. 



" The fibres of the middle layer are much more numerous, and follow the same di- 

 rection ; only they are more oblique, and are not all of them earned to the apex of the 

 heart. The inferior fibres only reach the apex, and are there confounded with the fibres 

 of the outer layers. Whilst the others, according as they become more superficial, 

 reach the posterior farrow, where the layer untwists itself, to form the two unequal 

 portions which compose the lower layer of each ventricle. 



" The lower layer of the right ventricle, which is much thinner than that of the left, 

 separates itself from the latter on a level with the posterior furrow, and is earned back- 

 wards, on the outside, before, and then within the ventricle which it immediately en- 

 velopes. All its bundles bencl from below upwards, and, crossing the direction of those 

 of the middle layer, are fixed, the upper ones, which are almost transverse, to the cir- 

 cumference of the auriculo-ventricular opening, and to the anterior part of the mouth 

 of the pulmonory artery the others, which are longer and more oblique, and which 

 form the right side of the septum, successively to the part of that orifice which is be- 

 tween the two ventricles, and to its posterior part. 



" The lower layer of the left ventricle, which is much thicker than that of the right, 

 arises like it from the middle laver, on a level with the posterior furrow. Its bundles 

 r^n from behind to before, between the two cavities, thus forming- the left side of the 

 septum, reach the anterior furrow, then, running from right to left, and from below up- 

 wards, they surround the ventricles ; and, crossing the line of the bundles of the middle 

 layer, are fixed successively, one by the side of the other, to the origin of the aorta, and 

 to the opening of communication between the ventricle and auricle, all the way to the 

 upper extremity of the posterior furrow. 



* The lowest bundles on each side alone follow a different direction. These bundles 

 after separating from the others, approach the centre of the corresponding ventricle, 

 and form the columnx carneae of the heart. 



" Thus all the fibres of the superficial layer take the form of a lengthened spiral, 

 which takes a direction from the base towards the apex of the heart, where the fibres 

 are confounded with those of the middle layer, after having made a turn or a turn and 

 a half. Those of the middle layer have the same form, the same general direction, and 

 the same origin ; but they are more oblique, and are so arranged, that one part only 

 of them reach the apex of the heart, whilst the greater part terminate at its posterior 

 furrow. Those of the last layer of each ventricle have still a spiral form, but the screw 

 takes the inverse direction, for the fibres stretch from the posterior furrow to the base 

 of the heart; and they do not reach that part until they have surrounded the corres- 

 ponding ventricle from right to left, crdfesing the line of the fibres of the two other lay- 

 ers. The septum is formed by the junction of the two lower layers with the addition 

 of a few bundles, which run from the apex of the heart, and appertain to the middle 

 and superficial layers, which are mixed together at that part. 



" The structure of the auricles is less regular. In general, the fleshy fibres pass from 



