1902.] ANATOMY OF THE CONDOR. 243 



plainly, as in other birds, inserted on to the surface of the 

 membrane covering the lung. Nevertheless, it appears to me 

 that possibly the conditions obtaining in these two kinds of birds 

 may give a clue to the origin of a portion of this musculature of 

 the lung. I have suggested ah"eady, in my former paper upon 

 the Condor, that the sheet of muscle enwi-apping the end of the 

 bronchus may be the remnant of an intrinsic syringeal muscle 

 altered in function in cori-espondence with the degenei'ation of 

 the syrinx itself. A second stage is seen in the male Sarco- 

 rhamphus, where the muscle is reduced to the one or two " tags " 

 which tie down the end of the bronchus to the lung-surface. 

 The final stage is shown in Gathartes, in which birds in both 

 sexes the " tags " of muscle are present and weU developed, but 

 have entirely lost all special relation to the end of the bi-onchus. 

 This, however, is at pi-esent a suggestion for the origin of those 

 muscles, the nature and distribution of which require, and have 

 not yet had, detailed attention in many groups of birds. 



The heart of the Condor has been dealt with by Gegenbaur ^ 

 and by myself ". We have both recorded the occurrence of traces 

 of the septal flap of the right auriculo-ventricular valve, which is 

 for the most part missing in Birds. I therefore examined with 

 particular interest the heart of the male Sarcorhamjyhus gryphus, 

 to the windpipe of which I have dii-ected attention above. 

 Gegenbaur found in a heart examined by himself " a fold .... 

 which is formed by a thickening of the endocardium " ; this fold 

 was found to run backwaixls " from the anterior origin of the 

 muscular valve." It is not altogether easy to follow the description 

 given by Gegenbaur, since it is unaccompanied with any di-awings. 

 I take it, however, that what Gegenbaur saw in the heart studied 

 by him was a prolongation of that part of the valve, arising to 

 the left of the great papillary muscle, tying the valve to the 

 free non-septal wall of the ventricle : to the left, that is to say, 

 when the right ventricle is opened and looked at from in front. 

 Now I have already brought forward reasons for considering that 

 this part of the valve, which appears occasionally to be rather 

 membranous in constitution and is always of thinner texture 

 than the larger half of the valve, is the equivalent of the septal 

 half of the valve in the Crocodile's heart ^. A further study of the 

 Crocodile's heart led Dr. Chalmers Mitchell and myself to the 

 same conclusion. What Prof. Gegenbaur therefore has been able 

 to place on record is a still gi-eater extension of this septal half 

 of the right auriculo-ventricular valve. In a vanishing structure 

 such fluctuations are genei'ally met with. 



In the corresponding valve of the Monoti'eme heart, Pi'of. 

 Lankester found considerable variations in the amount of the 

 septal half of the valve which was present ; and I do not doubt 

 that careful measurements would prove the same thing for the 



1 " Zur vergleichenden Anatomic des Herzens," Jen. Zeitschr. ii. 1866, p. 365. 



2 P. Z. S. 1890, p. 141. 



3 " On the Structure of the Heart of the Alligator," P. Z. S. 1895, p. 348. 



