694 



MR. F. E. BEDDARD ON THE 



[June 15, 



§ Heart and Vascular System. 



The cavity of the right ventricle of Tamandua showed two 

 interesting features which deserve comment. There is, in the 

 first place, a very strongly developed moderator band which is 

 represented in the annexed text-figure (text-fig. 222). This 

 consists of a somewhat slender muscular band wdiich arises just 

 below the great septal papillary muscle of the auriculo- ventricular 

 valve. The muscular band from the septal wall of the ventricle 

 enters this moderator band from above. On the posterior side it 

 seems mainly formed as a process of the endocardial lining. 

 Near to the free wall of the ventricle it separates into many 

 tendinous branches shown in the figure, which would take too 

 long a space to describe individually. These spread out in their 

 abundant ramifications and anastomoses over a considerable area 



Text-fig. 222. 



A portion oftlie heart of Tamandua, with the right ventricle opened to 

 display the moderator band ()».). 



of the free wall of the ventricle. A single tendinovis thread 

 arising near to but independently of the moderator band also 

 connects the septal with the free wall of the ventricle. Moderator 

 bands are not uncommon * in the right ventricle, and are known 

 in birds as well as mammals. It appears that a similarly situated 

 m.oderator band occvu's in the Great Anteater also. For in a 

 figure of the interior of the right ventricle of that animal, Sir E. 

 Ray Lankester has represented t a muscle cut ofi' short which 

 arises from the septal wall of the ventricle close to and behind 

 the chief mtiscle of the auriculo-ventricular valve. He has not, 

 however, given any description of this structure, with which 

 indeed he was not concerned in the paper quoted. The right 



* Cf. e. g. Biudo de Vecchi, Anat. Anz. xx. 1902, p. 374, where some literature is 

 cited. 



t P. Z. S. 1882, pi. xli. fig. 20. 



