188 MR. F. E. BKDDARD ON THE HEART OF APTERVX. [Feb. 17, 



2. On the Heart of Apteryx. By F. E. Beddard, M.A., 

 F.R.S.E.^ Prosector to the Society. 



[Eeceived February 17, 1885.] 



The structure of the heart of Apteryx has been described some- 

 what fully by Sir Richard Owen in his well-known memoir upon the 

 anatomy of the Southern Apteryx ' ; this account is illustrated by two 

 figures, one of which represents the heart in its entirety viewed from 

 the right side, while the other is a view of the same region of the 

 heart, with the wall of the right ventricle removed in order to 

 display the structure of the right auriculo-ventricular valve. 



The description given of the right auriculo-ventricular valve is as 

 follows : — 



"The principal deviation from the ornithic type of the structure 

 of the heart is represented in the valve at the entry into the right 

 ventricle (pi. lii. fig. 3). This is characterized in birds by its 

 muscularity and its free semilunar margin. In the Apteryx it is 

 relatively thinner and in some parts semitransparent and nearly 

 membranous ; a process moreover extends from the middle of its free 

 margin, which process is attached by two or three short chorda 

 tetidinecE to the angle between the free and fixed parietes of the 

 ventricle. We perceive in this mode of connection an approach in 

 the present bird to the mammalian typeof structure analogous to that 

 which the Ornithorhynchus, among Mammalia, offers, in the structure 

 of the same part, to the class of birds ; for the right auriculo- 

 ventricular valve in the Ornithorhynchus is partly fleshy and partly 

 membranous." 



The figure which illustrates this description is entirely in harmony 

 with it, but does not at all represent the structures observable in the 

 hearts o( Apteryx that I have myself studied. 



In a heart of Apteryx austraiis, which I found among the 

 Prosector's stores, the right-auriculo-veutricular valve is composed 

 of two halves which unite together at a point nearly opposite the 

 auriculo-ventriculiir aperture, and are connected there by a muscular 

 flap to the dorsal (free) wall of the ventricle. The right half is the 

 larger and arises chiefly from the free wall of the ventricle, partly, 

 however, from the septum and from the point of union of the septum 

 with the free wall ; it is of uniform thickness and muscular through- 

 out. The left halt" of the valve is considerably smaller; it arises 

 from the inter-ventricular septum and from the septum between the 

 ventricle and the auricle ; like the right valve, it is muscular through- 

 out with the exception of a very minute membranous portion lying 

 at the lower side of the valve ; this portion of the auriculo-ventri- 

 cular valve is not of uniform appearance like the left, but is foruied 



' Trane. Zool. Sue. vol. ii. \t. 'J.1'1. 



