PHARYNX AND LARYNX. 43 
go to two flaps, or one flap may have chorde from 
two papillary muscles. 
Cut through the right ventricular wall between two 
of the flaps to get a better view of their attachments. 
Note the reteculated structure of the ventricular 
walls—the columne carnee. 
b. THE Putmonary ARTERY. The portion of 
the right ventricular cavity leading into the pulmonary 
artery is known as the conus arterzosus and forms a 
funnel-like recess. The opening into the artery is 
guarded by three pocket-valves, the semzz-lunar valves, 
which can be exposed easily with a probe from the 
opening of the artery above. Cut through the 
conus and artery longitudinally to get a better view 
of the valves. 
c. THE MitraLt Vatve of the left ventricle 
guards the left auriculo-ventricular orifice. It resem- 
bles the tricuspid, with the exception that there are 
only two flaps or cusps. 
d. THe Aortic SEMI-LUNAR VALVES, three in 
number, have the same structure as those of the pul- 
monary artery. 
e. THE Coronary ARTERIES. Behind two of 
the aortic semi-lunar valves will be found the open- 
ings of the two coronary arteries arising from the base 
of the aorta. Runa probe into each and follow its 
course for some distance. 
3. The Trachea and Bronchi. Find the trachea as 
it enters the thorax. Dissect it toward the lungs. It 
divides into two large branches, the bronchi, one for 
each lung. If one of the bronchi is followed into the 
lung to which it is distributed it will be found to give 
off smaller bronchi at intervals, and these in turn give 
off still smaller branches, the whole system forming 
