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Show 1885.] MR. F. E. BEDDARD ON THE HEART OF APTERYX. 189 of a number of closely united fleshy columns. Just before the junction of the left half of the valve with the muscular flap already described two minute chorda tendinea connect it with the free wall of the ventricle between the attachments of the left half of the valve and the free muscular flap ; the two are fused almost immediately after their origin, and form a single excessively small fibrous band which is attached to a papillary muscle. I can find no trace of the chorda tendinea that Sir R. Owen figures arising from the lower margin of the valve and inserted towards the hinder end of the ventricular cavity ; the only structure at all similar is the slender fibrous band which I have described as connecting the valve with the free wall of the ventricle; this structure does not appear to me to be the same for reasons which I shall put forward in describing the heart of Apteryx oweni. With regard to the valve itself, it is not in m y specimen " in some parts semitransparent and nearly membranous ;" the thickness of the valve, which, except for a small portion on the left half is entirely muscular, is by no means less than that of any other bird with which I have had the opportunity of comparing it ; the very slight development of membrane on the left half of the valve close to its origin is clearly a matter of no importance, since I have found this same feature to be more marked in Eupodotis and in other birds. In short, my heart of Apteryx, as well as a specimen in the possession of Prof. Lankester, which he kindly allowed me to inspect, and another preserved in the Oxford Museum, present no differences of any importance from the hearts of other birds. Of the heart of Apteryx oweni I have been able to examine two examples, in both of which the right auriculo-ventricular valve has much the same structure. It only differs from that of A. australis in the presence of a stout muscular band arising from the septal wall of the ventricle and attached to its free wall close to the fleshy bridge which unites the free margin of the valve to the ventricular wall ; it gives off a short branch to the latter. This structure closely corresponds to the " moderator band " described by Prof. Rolleston in the heart of the Cassowary ; the chordce tendinea which I have described in the heart of A. australis probably represent the upper portion of the moderator band of A. oweni. I have examined a large series of hearts of birds with a view to discovering if there were any deviations from the normal type in the ria-ht auriculo-ventricular valve, but I can find none ; the only differences at all are in the left-hand portion of the valve, which is more or less membranous, and in a specimen of Eupodotis australis appears to be entirely so. Gegenbaur, however, speaks of a rudimentary septal flap in Sarcorhamphus 1. 1 Jen. Zeitschr. Bd. ii. p. 380. |
