10 DISSECTION OF THE DOG 



A group of lymph-glands will also be found in the inguinal region. 



Several vessels and nerves pierce the abdominal wall. Of these the circum- 

 flex iliac vessels and the lateral cutaneous femoral nerve are the most 

 conspicuous. They appear close to the angle of the ilium and are distri- 

 buted in the cutaneous muscle of the abdomen and in the skin over the 

 lateral proximal part of the thigh. A little cranial to the point of 

 appearance of the circumflex iliac vessels, the phrenico-abdominal artery 

 pierces the oblique muscle of the abdomen. Branches of the ilio-inguinal 

 and ilio-hypogastric nerves should also be noted and preserved. 



A. pudenda externa. — The external pudendal artery is generally a 

 branch of the deep femoral, but it may arise from a common trunk from which 

 springs the caudal epigastric artery as well. The origin of the vessel cannot be 

 examined at present. Crossing the spermatic cord medially, the artery runs 

 towards the umbilicus and supplies the inguinal lymph-glands, the prepuce, 

 and the surrounding skin. In the female it is larger and furnishes blood to 

 some of the mammary glands. 



N. speematicus extekntjs. — The external spermatic nerve is a part of the 

 genito-femoral nerve. Appearing through the abdominal wall along with the 

 external pudendal vessels, it crosses the spermatic cord and is expended in the 

 external genital parts, or the mammary glands, and the skin of the inner part 

 of the thigh. It is sometimes connected with the ilio-inguinal nerve. 



M. obliqutjs externus abdominis. — The external oblique is the most 

 superficial muscle of the abdominal wall. Its origin is by digitations from 

 the ribs from the fifth or sixth to the last, and from the lumbo-dorsal fascia. 

 The muscular fibres run in a caudo- ventral direction as far as the border of the 

 straight abdominal muscle. Here they give place to an aponeurosis which 

 is attached to the linea alba. An important part of the aponeurosis stretches 

 from the lateral angle of the ilium to the pubis near the symphysis. This 

 constitutes the inguinal ligament ofPoupart (ligamentum inguinale [Pouparti]), 

 in association with which is the superficial opening of the inguinal canal. 

 Opposite this opening the pectineus muscle takes part of its origin from the 

 inguinal ligament. At the same point a thin reflection of the aponeurosis to take 

 part in the formation of the scrotum should be noticed. Medial to the inguinal 

 canal, i.e. in the pubic region, the aponeurosis is thin and mixed with fibres from 

 the other abdominal muscles. 



From the aponeurosis of the oblique muscle a thin, ill-defined sheet is 

 reflected onto the medial aspect of the thigh. 



M. latissimus dobsi. — As its name indicates, this is a very broad muscle 

 covering the dorso-lateral part of the thorax. Its origin is from the lumbo- 

 dorsal fascia, by means of which it is attached to the spinous processes of the last 

 seven thoracic vertebrae, and by fleshy strips from the last two or three ribs. 

 Its insertion is by a flattened tendon into the crista tuberculi minoris of the 



