THE CAT 233 



Slit open the dorsal wall of the left auricle, but without cutting 

 the pulmonary veins. Note the three openings of the pulmonary 

 veins, and the large auriculo-ventricular aperture. 



Open the left ventricle by slitting the aorta and continuing the 

 incision through the ventricle to the apex of the heart, and study 

 the interior. Note the thickness of its walls. The auriculo- 

 ventricular aperture is guarded by the bicuspid, or mitral, valve, 

 which consists of two distinct flaps joined with the ventricular 

 wall by chordae tendinae. The opening into the aorta is guarded 

 by three semilunar valves, one of which is dorsal and the other 

 two lateral. Note the two prominent muscular ridges, the columnae 

 carneae, in the wall of the ventricle. 



Exercise 22. Draw a diagrammatic view showing the four cavities of 

 the heart and their apertures and valves. 



Cut off the apex of the heart by a transverse incision a quarter 

 of an inch from the end, showing the two ventricles. 



Exercise 23, Draw the cross section. 



Exercise 24. Draw a diagram showing the entire vascular system. 



The Mouth and the Pharynx; the Salivary Glands. Skin the 

 head. Five pairs of salivary glands are present, all of which open 

 into the mouth. 



The parotid glands are the largest. Each is situated just be- 

 neath the skin and immediately below the ear; its duct passes 

 through to the inner surface of the cheek, where it opens into the 

 mouth opposite the last premolar tooth. 



The submaxillary glands are situated just below and behind 

 the parotids. The duct of each runs forward, and opens at the 

 end of a papilla in the forward part of the floor of the mouth, 

 near the median line. 



The sublingual glands are situated in front of the submaxillaries 

 and in contact with them. The duct of each passes forward, and 

 opens into the mouth at the apex of the same papilla. 



The molar gland extends from just beneath the angle of the 

 mouth posteriorly ; it is very small and opens into the mouth by 

 a number of ducts. 



