224 



MR. F. E. BEDDARD ON THE 



[Feb.l, 



referred to), the rudimentary orifice is thickened along one side ; 

 b is the aortic orifice, a that in the pulmonary artery. 



Text-fig. 22. 



The aorta and pulmonary artery of Hippopotamus opened up to show the 

 vestigial orifices (a & b) of the ductus Botalli. 



The right ventricle fully opened is shown in text-fig. 23. It 

 will be observed from the very accurate figure that the free wall 

 of that ventricle is not sculptured into columnar carnosse, but 

 merely presents an honeycombed appearance. It is in fact only 

 unevenly pitted with variously sized excavations which acquire, 

 near to the attached wall of the ventricle, some approach to the 

 more usual arrangement of trabecule. The auriculo-ventricular 

 valve itself was markedly tricuspid, and it is shown in the text- 

 figure not in its normal position. For the cutting and reflection 

 of the free wall of the ventricle has carried with it the muscles 

 attached to the middle flap of the valve, the infundibular cusp of 

 human anatomy. On the extreme left the valve is attached to 

 the septal wall of the ventricle in a way which is not universal 

 among Mammals. There is, in fa,ct, a thick and well-marked 

 papillary muscle in this situation which is shown in the figure, as 

 are the other papillary muscles, as striated longitudinally, to 

 distinguish them more definitely from the walls of the ventricle. 

 This septal papillary muscle is quite short and very stout. 



The anterior papillary muscle is rather complex. Its actual 

 origin from the ventricular wall is marked by the letter " A " 

 towards the right of the drawing (text-fig. 23), and a portion of 

 it also arises from the neighbouring cut edge marked " B." The 

 actual course of the papillary muscle and its subdivisions is 



