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Show 1894.] TISCERAL ANATOMY OF ORNITHORHYNCHUS. 721 u n' "^Ut D.e*;ween the apparent end of this flap and the muscle e was a slight thickening, ligamentous in texture, of the interventricular wall of the heart. I hardly noticed this until I had examined the second heart. In the latter the septal flap of the Fig. 3. Heart of Ornithorhynchus, with right ventricle opened. sp, septal flap of valve. a, a', severed muscles of outer valve-flap. right auriculo-ventricular valve was completely developed. It was tied down to the interventricular septum by two slight papillary muscles, which, however, did not, as in the case of the other half of the valve, at all invade the tendinous tissue of the valve. They were attached to its edge merely by the tendons. This septal half of the valve lay close to the interventricular wall, as, indeed, is generally the case among mammals ; in the first of the tAvo hearts it was so little detached from the ventricular Avail as almost to suggest a case of cardiac disease rather than a normal structure. But the state of affairs in the second heart showed plainly how it was necessary to interpret the first heart. It will be noticed that m y observations agree entirely Avith those of Gregenbaur, particularly in the case of the first heart, in which (to quote from Prof. Lankester's translation of Gegenbaur's paper) " no trabecular pass PROC. ZOOL. Soc-1894, No. XL VIII. 48 |
