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Show 240 PROF. LANKESTER ON THE HEART OF APTERYX. [Mar. 3, of looking at Owen's specimen of the heart of Apteryx, which is now in the Museum of the Royal College of Surgeons, No. 923 B. b. and that it certainly differed altogether, as regards its right cardiac valve, from an ordinary bird's heart, and from the Apteryx-heart dissected by him. Mr. Beddard remarked, as Owen had done himself, that the valve in this specimen in the College of Surgeons was very similar to the right cardiac valve of the Monotremata. It occurred to m e that possibly Sir Richard Owen had made an unfortunate mistake at the time of dissecting his Apteryx, and that since he had at the same time specimens of Ornithorhynchus under examination, side by side with the Apteryx, the heart of one of the latter might, by the inadvertency of some assistant or attendant, have been exchanged for the heart of the former. Accordingly on Feb. 18th I requested Prof. Charles Stewart to allow me to remove from its bottle, and closely examine the specimen 923 B. b., labelled "Heart of Apteryx australis" (so placed and labelled, so far as I have been able to ascertain by inquiry, under the direction of Prof. Owen). The figure in the Society's 'Transactions' does not represent the appearance of this heart, inasmuch as three musculi papillares are figured, and are described as " chordae tendineae," whilst only two (the great anterior and the right) are obvious in the preparation. That is, however, a matter of detail which Prof. Owen regarded as liable to variation, since he says that two or three chordae tendineae are present, and in his paper on Apteryx he speaks of having dissected two specimens. On removing the heart from the bottle in Prof. Stewart's presence, I was able to point out to him that the aortic arch of this supposed heart of Apteryx has a sinistral and not a dextral flexure. I also found that the auricles and the relatively small jugular sinus are identical with that of Ornithorhynchus, and unlike the auricles and large veinous sinus of any bird. I found, further, that the arrangement of muscle and membrane in the right cardiac valve is precisely (not only approximately) similar to that described by me in Ornithorhynchus, and figured in the ' Proceedings ' of the Society for 1882, pi. xl., and also in 1883, pi. iii. The shape of the whole heart, the shape of the right ventricular cavity, and the markings of its surface (rudimentary columnae carneae) are precisely of the same character as in the nine specimens of Ornithorhynchus-hearts examined by me. I have no hesitation in stating that the heart, specimen No. 923 B. b., in the Museum of the Royal College of Surgeons, is not the heart of an Apteryx, but the heart of an Ornithorhynchus paradoxus. This being the case, the discrepancy between the observations made independently by Mr. Beddard and by m e upon the structure of the right cardiac valve of Apteryx, when compared with the statements made forty years ago by Sir Richard Owen, is accounted for. Sir Richard Owen did not examine the heart of Apteryx, but by an accident occupied himself with the heart of an Ornithorhynchus which he mistook for the heart of that bird. |