52 Physiology. 



these flaps hang down along the walls of the ventricles so 

 that on opening the heart one would see only a single 

 cavity in each half of the heart. 



The Aur-vent Valves. Since these valves are between 

 the auricles and the ventricles they are often called the 

 auriculo-ventricular valves. Nearly every one knows of the 

 town named Pen Mar on the line dividing Pennsylvania 

 from Maryland. The meaning of the name is clear. And 

 any one can tell where Texarkana must be. So for con- 

 venience we shorten auriculo-ventriculaj* to aur-vent, and 

 when speaking of the aur-vent valves we know, without 

 having to stop and think, that they are between the auricles 

 and ventricles. 



The Semilunar Valves. From the base of the right 

 ventricle arises the pulmonary artery. Within its base, 

 just as it leaves the ventricle, are three pocket-like valves, 

 like "patch-pockets." They are in a circle, with their 

 edges touching, and thus surround the opening, with their 

 mouths opening away from the heart. A similar set of 

 valves are within the base of the aorta, which arises from 

 the left ventricle. Both these sets of valves are called 

 semilunar valves. As they are between the ventricles and 

 the arteries they are sometimes called the ventriculo-arterial 

 valves. And this may be shortened to vent-art valves. 

 (See Fig. 33-) 



Dissection of the Heart. No description (or even pictures) can 

 give a clear idea of the heart. A good model will be of some assist- 

 ance. But the heart itself should be examined carefully and then dis- 

 sected. The heart and lungs of a sheep should be obtained (ask the 

 butcher to save the "pluck," i.e. the heart and lungs taken out together). 

 The relations of the heart to the lungs and other organs should first 

 be studied, and then the pericardium opened. Observe the outside of 

 the heart, and then cut the heart open to see the points given in the 



