DISSECTION OF THE PERINEUM. 1069 



duct (p. 487). The thoracic duct may be followed, with the concurrence of 

 the dissectors of the head and neck, to its termination in the angle of 

 junction of the left internal jugular and subclavian veins ; and, with the 

 assistance of the dissectors of the abdomen, it may be also followed down to 

 its commencement under the crus of the diaphragm. The sympathetic nerve 

 with its chain of ganglia, is now to be traced over the heads of the ribs and 

 the vertebral column : its communications with the intercostal nerves are to 

 be made out, and the splanchnic nerves arising from it dissected (p. 693). 



The upper surface of the diaphragm having been cleaned with the knife, 

 the dissectors of the thorax will examine along with those of the abdomen 

 the anatomy of this muscle, directing their attention to its various muscular 

 and tendinous parts, and to the apertures for the passage of the aorta, gullet, 

 and vena cava infeiior, and observing the distribution of nerves and blood- 

 vessels in its substance (p. 243). 



6. Articulations. When the dissection of the rest of the thorax has been 

 completed, the dissectors will, if the subject be favorable, make an examina- 

 tion of the articulations of the vertebral column and ribs (p. 121). Let 

 them study, in particular, the anterior and posterior common ligaments, the 

 intervertebral substance, the ligamenta subflava of the arches, the form and 

 movements of the articular processes, and the various costo- vertebral, costo- 

 trans verse and other ligaments. In doing this, the dissectors should make 

 an attentive examination of the nature and extent of the movements of the 

 different ribs, and the manner in which they are influenced by the move- 

 ments of the vertebral column. 



IV. ABDOMEN AND PELVIS. 



The right and left sides of these regions constitute each a part. Their 

 dissection should not be completed in less than four or five weeks. It com- 

 prehends the examination of the perinaeum and genital organs, the abdominal 

 parietes over the whole of the external oblique muscles, extending in front 

 to the linea alba and below to Poupart's ligament, the viscera and deeper 

 parts of the abdomen and pelvis, and the lower surface of the diaphragm. 



1. Perinceum. If the subject be a male, the first day on which it is in 

 the rooms will be set apart for the dissection of the perinseum ; and of this 

 opportunity the dissectors of the abdomen must be prepared to avail 

 themselves. A lithotomy staff is to be passed into the bladder, and, the 

 hands and feet having been tied together, the subject is to be placed in the 

 same position as for the operation of lithotomy, near the edge of the table. 

 A block is then to be placed below the pelvis, and the scrotum is to be tied 

 up to the handle of the staff. The body may, however, be still more con- 

 veniently maintained in the proper position, as is done in some schools, by 

 means of a simple frame with two upright spokes, behind which the limbs 

 are placed while the perinteum is projected forwards between them. A 

 careful incision is to be made in the middle line from the back of the 

 scrotum to the anus, and, being carried round the margin of the anus, is to 

 be prolonged as far as the coccyx ; while a transverse incision is to be 

 directed across the middle line in front of the anus from one ischial 

 tuberosity to the other. Let the dissector reflect the flaps of skin, exposing 

 the external sphincter, and clear out the fat completely from the ischio- 

 rectal fossa of the left side, taking care not to injure the reflection of fascia 

 which bounds it in front in a line with the central point of the perinseum ; 

 and let him study the wall* of the fossa (p. 261). On the right side, 



