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Show 1895.] ON THE HEAET OF THE ALLIGATOE. 347 parietes by delicate muscular threads, which may be compared with the papillary muscles of the valves of the mammalian heart. In spite of the luminous investigations of Prof. Lankester upon this matter, and of the previously expressed views of one of us \ we cannot regard the morphological relationship of the different parts of the valve of this animal and that of the bird as thoroughly cleared up. Fig. 3. Heart of the Common Fowl, opened to display the cavity of the right ventricle. x, x. Cut surfaces. b. Right part of the valve identified by us with right part of valve in Alligator (fig. 2, d). c. Septal part of valve identified by us with Alligator's septal flap (fig. 2, c). a. Muscular bridge identified by us with structure shown in fig. 2, e. The view taken by Prof. Lankester, and generally accepted, is that the entire fleshy valve of the right (b) ventricle of the Bird's heart corresponds to one half only of the complete valve of the Crocodile2 and of the M a m m a l ; in the Bird it is held that the septal half of the valve is quite absent and not even represented by rudiment. Now, if we consider the Bird's heart in a position exactly corresponding to that of the Alligator as shown in our drawing (fig. 3), this comparison seems to be inexact. The larger half of the valve lies on the right side, and is of course entirely fleshy; in the Ostrich, which we have recently had an opportunity of examining and which was typically avian in every respect, this half of the valve was slightly sculptured on its right face near to the origin from the walls of the heart. A comparison in this matter with the corresponding face of the same valve in the Alligator will 1 F. E. Beddard, " On the Heart of Apteryx," P. Z. S. 1885, p. 188, and " Notes on the Anatomy of the Condor," P. Z. S. 1890, p. 142. 2 " Bei Vogeln a m rechten Ostium die mediale endocardiale Taschenkhippe der Krokodile vollstandig geschwunden," Reise, Morph. Jahrb. 1890, p. 80. |