408 ADVANCED PHYSIOLOGY 



carefully and remove most of the right ventricular wall, but do not get 

 within an inch of the semilunar valves of the pulmonary artery. At this 

 point the tricuspid valve, chordae tendinse, and papillary muscles of this 

 side of the heart are fully exposed. If the conveniences of a water faucet 

 and sink are at hand, slip over the faucet opening a rubber tube (about a 

 yard long) in the end of which is a piece of glass tubing, both ends of which 

 have been made smooth by heating. Insert the tube between the semilunar 

 valves and fill the artery with water till it swells under the pressure ; when 

 very full, quickly draw out the tube ; the semilunar valves will completely 

 close and prevent the escape of water. If the specimen is held up to the 

 light, the position of the valves and their perfect closure of the aperture 

 can be clearly shown. 



The action of the other type of heart valve can be shown as follows : 

 First follow the aorta downward into the substance of the base of the heart, 

 till the two coronary arteries are found ; these must be tied off (with a 

 broad cord, as the tissues are soft and easily cut by a small ligature) or the 

 rest of the experiment will not succeed. Now cut off the top of the left 

 auricle ; the peculiar internal structure of an auricle is thus seen. Clamp 

 off the aorta, as near its end as possible. Thrust the water tube down 

 through the auriculo- ventricular opening, and fill with water. The left 

 ventricle will first fill, and from there the water will go into the aorta and 

 fill that. In the meantime, the two flaps of the mitral valve have risen 

 and perfectly closed the entrance to the ventricle. When the internal 

 pressure of the water has become considerable, draw out the tube, and the 

 heart can then be manipulated to show better the valves in their closed 

 position. After this, the ventricle can be cut open, the thickness of its 

 walls compared with that of the right ventricle, the extreme thinness 

 of the wall at the apex of the heart shown, and any other points which 

 the instructor wishes to bring out. 



Do not fail to cut out the semilunar valves and place in formalin for 

 future use. 



Pages 143. To one end of a piece of thin rubber tubing about three 

 feet long attach a syringe bulb by means of which water can be forced 

 through the tube. Into the other end of the tube insert a glass cannula, 

 drawn fine, in imitation of a capillary. As the bulb is pressed rhythmi- 

 cally a regular pulse can be felt in the tube by holding it between the thumb 

 and finger. It can be shown a large class by connecting the short arm of a 

 horizontal lever with the tube by means of an upright strip of wood, or 

 other material ; see figure on opposite page. The amount of " pulse " or 

 change in diameter of the tube will be increased in proportion to the 

 differences between the lengths of the arms of the lever. 



