144' MR. F. E. EEDDARD ON THE [Mar. 18, 



by its insertion on to the valve the junction between its fleshy and 

 membranous portions ; ou the right side the valve is muscular, on 

 the left it is membranous. If this comparison be just, it seems to 

 follow that the septal portion of the right auriculo-ventricular valve 

 is not entirely wanting in the Bird's heart, as it has been generally 

 stated tobe^. In view of the possible comparison between that 

 part of the Bird's valve which lies to the rigiit of the fleshy bridge 

 (when the heart is placed on its left side with the apex downwards) 

 and the membranous or "septal" flap, as it has been better termed 

 by Lankester ', of the Crocodile's heart, it is important to bear in mind 

 the following fact, that this part of the valve in the Bird's heart, 

 though sometimes as thick and fleshy as the rest, is often thin and 

 delicate and sometimes partially membi-anous. 



Furthermore, the trabeculfe uniting the valve with the parietes 

 have )iot entirely disappeared from the Bird's heart. Gegenbaur him- 

 self implies that they have by the quotation on p. 143. But in many 

 birds, for example in the heart of Burmeister's Curiavaa (Chunga bur- 

 meisteri) shown in the accompanying drawing (woodcut fig. 2), the 

 margin of the valve is tied down to the free ventricular ivall by several 

 delicate muscular or tendinous threads in addition to the laryc jleshy 

 bridge, which is a constant structure in the bird's heart. 



Next, as to the partial persistence of the septal flap in the Condor's 

 heart. In one specimen which I dissected some years ago, I observed 

 no traces whatever which could be compared to a septal flap. In 

 the specimen which is more particularly described in the present 

 paper there were a series of tiny yellowish spots and vesicles a little 

 way from the posterior margin of the atrio-ventricular orifice, which 

 formed a line occupying a position identical with that which would 

 be occupied by a septal part of the valve if it were present. The 

 structures in question seem to me to be probably pathological ; but it 

 is a significant fact that they are situated along a line which would 

 correspond to the insertion of a septal half of the valve ; I can, 

 indeed, quite believe that in many Condor hearts a thickening such 

 as that described by Gegenbaur exists, which is possibly, as a rudi- 

 mentary structure, especially prone to disease. 



In Chunga burmeisteri (see woodcut fig. 2) a band of muscles 

 connects the fixed and free wall of the right ventricle ; from this 

 are given oft' several threads connected with the supplementary mus- 

 cular bands which tie down the edge of the valve to the free wall of 

 the ventricle. This muscular pillar is, I presume, the equivalent 

 of the moderator band in the heart of Casuarius described by Prof. 

 RoUeston. It has been, I think, suggested somewhere that this 

 moderator baud is the equivalent of part of the septal portion of the 



^ Owen (article " Aves," Todd's ' Cyelopcedia of Anatomy,' vol. i. p. 331) has 

 erroneouslj- compared, as Gegenbaur pointed out, this fleshy bridge of the Bird's 

 heart with the entire membranous pai't of the valve in the Crocodile's heart. 

 I find that Sabatier has apparently made the same comparison as that urged in 

 the text. 



- " Ou the Right Cardinal Valve of Echidna and of Ornithorhynclms," P. Z. S. 

 1883, p. 831 ct i^eq. pi. iii. fig. 1, 3, 4, pi. iv. figs. 5, 6. 



