DISSECTION OF THE DOG 



are lodged. It lies between the thighs, and forms a rounded prominence 

 crossed in a cranio-caudal direction (generally obliquely) by a shallow groove 

 in which a faint line, the raphe scroti, may be detected. The skin of the 

 scrotum is thin and provided with comparatively few hairs. 



Dissection. — Make an incision through the skin along the raphe of the 

 scrotum, and expose the underlying tissues. 



nn. cervicales 



n. thoracalis longus 



n. thoraco-dorsalis 



phrenicus 

 m. pecioralis superficfalis 



m. brachio-cephalicus 



ti. musculo-cutaneus 



n. suprascapular 



^nn. subscapulars 



To m. pectoralis profundus 



v N n. axillaris 



nn. medianus el itlnaris 

 *- n. railialis 

 Fig. 2. — Diagram of the brachial plexus. 



The wall of the scrotum can be resolved into three layers. Of these the 

 most superficial consists of skin. Under this is a fibrous tissue known as the 

 tunica dartos, which, with its fellow of the other side, forms the median septum 

 between the two scrotal cavities — the septum scroti. 



Removal of the dartos exposes the third layer composed of a fascial tunic 

 lined within by a serous membrane. The fascia is continuous with that 

 covering the deep face of the transverse abdominal muscle, and is in the form 

 of a pear-shaped sac the narrow end of which is connected with the superficial 

 end of the inguinal canal. Along the dorsal side of the narrower part of the 

 sac there is a muscular slip, the external cremaster muscle (m. cremaster externus), 

 associated with the internal oblique muscle of the abdominal wall, on the one 

 hand, and terminating, on the other hand, in an aponeurosis within the 

 substance of the wall of the scrotum. 



