n8 



THE CIRCULATION. 



Fig. 39*- 



Mr. Savory has clearly shown that this pressure of the 

 blood is not entirely sustained by the valves alone, but in 

 part by the muscular substance of the ventricle. Availing 

 himself of a method of dissection 

 hitherto apparently overlooked, 

 namely, that of making vertical 

 sections (fig. 39) through various 

 parts of the tendinous rings, he 

 has been enabled to show clearly 

 that the aorta and pulmonary 

 artery, expanding towards their 

 _ 3 termination, are situated upon the 

 outer edge of the thick upper border 

 of the ventricles, and that conse- 

 quently the portion of each semi- 

 lunar valve adjacent to the vessel 



passes over and rests upon the muscular substance being 

 thus supported, as it were, on a kind of muscular floor 

 formed by the free border of the ventricle. The result of 

 this arrangement will be that the reflux of the blood will 

 be most efficiently sustained by the ventricular wall.f 



The effect of the blood's pressure on the valve is, as said, 

 to cause their margins to meet in three lines radiating from 

 the centre to the circumference (7 and 8, fig. 38). The con- 

 tact of the valve in this position, and the complete closure 

 of the arterial orifice, are secured by the peculiar construc- 

 tion of their borders before mentioned. Among the cords 

 which are interwoven in the substance of the valves, are 

 two of greater strength and prominence than the rest ; of 

 which one extends along the free border of each valve, and 



* Fig. 39. Vertical section through the aorta at its junction with 

 the left ventricle. I. Section of arterial coat. 2. Section of valve. 

 3. Section of ventricle. 



t Mr. Savory's preparations, illustrating this and other points in 

 relation to the structure and functions of the valves of the heart, are in 

 the museum of St. Bartholomew's Hospital. 



