RECAPITULATION. (Vid.the diagramfig.283.) We commence tracing the fibres of the heart from its very centre. The fibres, cc, from the two carncx columnw of the left ventricle, Ly, are joined by the fibres, a, from the rope an, after those fibres of the rope have expanded and formed the internal layer of the septum S ; in winding round the axis of this cavity they blend together as the initial letters can indi cate. The inmost of these fibres descend as far as the apex, where they twist sharply round and close the cavity, by which means they construct the apex, and become the superficial fibres of the heart. But the chief bulk of this mass of blended fibres makes a spiral sweep from left to right round the axis above the apex; and when it has described two circles, cac, it splits at the anterior edge of the septum into two bands, one being considerably longer than the other. The longer first makes one circle round the left ventricle, then another, enclosing both ventri cles. In making the first circle it passes through the septum forming its middle layer, and on reaching its posterior edge it receives from the pulmonary artery accessory fibres, which have crossed over the cavity of the right ven tricle, forming the inmost layer of its right or proper wall, and fibres from one of the curlew column of this ventricle, and from the aorta, being marked CITA. The accessory fibres are not represented, as they would have ren dered the diagram complicated and unintelligi ble ; but they are indicated by their initials being added in the lettering of the bands. This band in question may now be traced round the middle third of the left ventricle advancing towards both the base and the outer surface of the heart; on completing its first circle it arrives again at the anterior edge of the septum, receives another fascieultis of fibres from the aorta, and is marked CPCAA. it is then seen to take its course round the base and in front of the right ventricle. As it passes by the right aspect of the aorta,it again receives from it a faseieulus of fibres, and is lettered CPCA A A ; on reaching the posterior edge of the septum, it is further augmented by two accessions of fibres, one from the aorta at its posterior aspect, and the other from the middle Payer of the septum. This combination of
fibres from various sources is indicated by the combination of their initial letters, CPCA AA A C. It should be borne in mind that C large is the synalepha of CRC—the initials of the primitive mass of blended fibres. This band, in passing along the base of the left ventricle, makes at first a gentle twist of its fibres form ing the brim of this chamber; it afterwards makes a sharp twist and assumes the form of a rope, by which means its fibres are transferred to the interior of the ventricle. In descending this chamber, they expand again into a layer, and wind spirally round its cavity, first forming the internal layer, a, of the septum, and then associating with the expanded fibres of the two carnew columns, and thus arrive at the points front which we commenced tracing them. We now return to the anterior edge of the septum, S, in order to trace the shorter band. At this part the primitive mass of blended fibres splits into two bands : the longer passes behind the right ventricle through the septum as already described ; the shorter passes in front. The shorter first receives a considerable accession of fibres from the right surface of the septum, which pass down from the aorta, and from the two carnew columnw springing from this sur face : it is lettered CA CC ; it describes one spiral circle round both ventricles. It first passes over the lower half of the right ventri cle, forming the apicial band of the middle layer of its proper wall, and then round the left ventricle in an oblique direction to the base, and terminates at the aorta near the anterior coronary track, having completed its spiral circle round the heart.