Heart of Testudo Indica. 323 



is thicker than any other part, and is furnished with larger muscular 

 fibres or bands passing across in different directions ; those in the au- 

 ricle generally running from the opening into the ventricle, upwards. 

 These fleshy columns are often more than an inch long, and can be ea- 

 sily raised from the side of the auricle. The coronary vein opens into 

 the sinas venosus above the valves. The auricles open into the ventricles 

 by separate passages on each side of the septum, this part of the heart 

 being very much contracted, so as to form an isthmus between the auri- 

 cles and ventricles, each when distended passing outwards far beyond it, 

 the auricles extending, however, farther than the ventricles. 



The heart is flat, and the walls of the ventricles are so very thick as 

 to leave but little cavity between them : the ventricles measuring five 

 inches from edge to edge, the cavity not more than an inch and an half. 

 The parietes of the left side being much thicker than those of the right, 

 the proportion of cavity is so much the less. On the outside or sur- 

 face the muscular substance is firm and smooth, but on the inside it 

 very m\ich resembles a sponge in appearance, particularly in the left 

 ventricle ; the right, although equally partaking of this structure, hav- 

 ing within it a more marked muscular or fleshy substance, acting ap- 

 parently as a valve to the pulmonary artery, and partly as an imperfect 

 septum, wiich runs from below upwards, and rather from left to right. 

 The cavitits of the ventricles are very small, not containing one twen- 

 tieth part asmuch as the auricles ; the spongy walls taking up the whole 

 space, excejt at the upper part, under the termination of the septum of 

 the auricles ; which, if continued downwards, would have also formed 

 a septum for he ventricles. At this spot there is a distinct and clear pas- 

 sage, throughwhich the finger can be passed from one side or ventricle 

 to the other. This is covered above by a valve on each side, extending 

 from the edgeof the septum of the auricles. These two valves falling 

 down when the ventricles dilate, and the blood comes in from the au- 

 ricles, nearly toich each other and close up this opening between the 

 ventricles ; an( when the ventricles contract and push up these 

 valves, they ctse the opening between the auricles and ventricles. 

 The right side of the heart is furnished with a very distinct semi- 

 circular muscle towards the outside of the immediate passage between 

 the auricle and ventricle, and above the valve, which contracts this 

 passage, and wih the valve, completely closes the opening. On 



