CIRCULATORY SYSTEM 51 



remnant of the structure which is further developed in the 

 crocodile.' 



I have, since that sentence was written, examined 

 the heart of a condor, in which was found along a line corre- 

 sponding to where the nap would be, were it present, ' a 

 series of tiny yellowish spots and vesicles . . . probably 

 pathological,' but perhaps, like other pathological structures, 

 associated with a rudimentary structure. With this excep- 

 tion no trace has ever been found of a septal flap other than 

 the small flap already described. 



The left ventricle of the bird's heart has an auriculo- 

 ventricular valve, which is completely membranous, and is 

 tied to the parietes of the ventricle by tendinous threads 

 attached to papillary muscles. 



There is one more structure occasionally present in the 

 right ventricle of the bird to which we must direct attention 

 before leaving the matter. The late Professor ROLLESTON, 

 in his Hunteriaii lecture, described and figured in the heart 

 of the cassow r ary a muscular pillar uniting the free and 

 fixed walls of that ventricle, to which he gave the name of 

 moderator band. This structure occurs in a few r other birds 

 -for example, in Clinnga Burmeisteri, where it has been 

 figured. In the latter bird, however, there are two muscular 

 bridges, which run in the same direction. One of them is also 

 connected with the muscle tying the auriculo-ventricular valve 

 to the free wall of the ventricle. This may conceivably be a 

 rudiment of the septal half of the valve lying to the right side 

 of the heart. In any case these moderator bands, which 

 are also found in deer and in other running animals, seem 

 to be, according to ROLLESTON'S suggestion, a mechanism 

 for increasing the power of the ventricle to contract, and 

 thus ensuring a more rapid and regular flow of blood into 

 the lungs. It is characteristic, where it occurs, of running 

 animals. 1 



1 For other facts about the avian heart see A. SABATIEK, ' Etudes sur le 

 Cceur,' &c., Ann. Sci. Nat. (5), xviii. 1873, art. No. 4 ; F. R. GASCH, ' Beitriige z. 

 vergleichenden Anatomie des Herzens,' Arch. f. Naturg. liv. 1888, p. 119 ; 

 C. ROSE, 'Beitrage zur vergleichenden Anatomie des Herzens der Wirbelthiere,' 

 Morph. J.B. xvi. 1890, p. 27. 



E 2 



