PRACTICAL DIRECTIONS. 455 
3. Examine the cervix uteri and os uteri (p. 266). 
4. Introduce a probe through the neck of the bladder and note 
its emergence into the urogenital sinus. 
5. Find the end of the clitoris (p. 267), and its prepuce, and then 
dissect the integument carefully from about the external opening of 
the urogenital sinus and note an external sphincter of the sinus 
(M. levator vulvze) (p. 272, and Fig. 114), equivalent to the levator 
scroti in the male and continuous with the external sphincter ani. 
6. Find (if possible) the corpora cavernosa of the clitoris 
(p. 267) and the ischiocavernosi muscles (p. 269). 
DISSECTION OF THE CIRCULATORY SYSTEM. 
I. Toe Heart (p. 274, and Figs. 115-117). 
Use the heart from the specimen dissected for the muscles, or 
from the specimen on which the viscera were studied. 
1. Study the outside (p. 275, and Figs, 115 and 116), and learn 
to recognize all parts. Find the pulmonary veins (p. 275, and Fig. 
116, g, 2, 7) and cut them, thus separating the heart from the lungs. 
2. The Pericardium (p. 279). Ina specimen the thoracic con- 
tents of which have not been injured, dissect the mediastinal septum 
from the pericardial sac and remove fat about the great blood-vessels 
so as to expose them all fully. Study their relations. Prick and 
inflate the pericardium. Slit it lengthwise over the ventricles and 
reflect it so as to expose its contents. Study the attachment of 
serous and fibrous layers to the heart and their relation to one 
another. 
3. In dissecting the heart follow the course of the blood, study- 
ing each cavity with the aid of the descriptions (pp. 275-279) as you 
proceed. Dissect as follows: 
a. Remove the dorsal wall of the right auricle (p. 275) and of its’ 
appendage except that part of it to which the venz cave are 
attached. 
6. Introduce the probe from the right auricle into the right ven- 
tricle, and feel with the probe the line along which the ventricular 
wall joins the septum. Cut along this line so as to turn back the 
ventricular wall as a flap, which remains attached at the base of the 
ventricle. 
c. Introduce a probe through the conus arteriosus into the 
pulmonary artery and cut along the probe. 
d. Remove the dorsal wall of the left auricle and its appendage, 
but do nof remove that part to which the pulmonary veins are 
attached. 
e. Make a longitudinal incision beginning at the apex and divari- 
cate the lips of the cut as you pass toward the base, thus avoiding 
injury to the lateral flap of the bicuspid valve. Without injury to 
the flap or the columnz carne, remove the heart-wall at the sides of 
this incision near the base of the ventricle, as much as necessary to 
expose the cavity. 
