THORAX AND ABDOMEN OF THE HORSE 69 



or less amount of fat is contained in it, but it should be noted that no 

 fat occurs beneath the skin of the teat. 



The deep fascia is more definite. It forms a yellow elastic envelope 

 for each gland, and serves to connect it with the elastic tunic of the 

 abdominal wall by a suspensory ligament (ligamentum suspensorium). 

 Where the two glands meet, the deep fascia forms a septum between 

 them. Further, it is continuous with the septa between the lobes of 

 glandular tissue of which the organ is composed. 



An incision into the substance of the mamma reveals a yellowish 

 pink granular tissue of lobulated character ; and, if the gland is active, 

 milk exudes freely from the cut surface. 



Associated with the mammary glands are numerous veins of 

 considerable size with frequent anastomoses. These communicate with 

 two main veins — cranial and caudal — on each side of the body. The 

 cranial vessel should be sought between the mammary gland and the 

 wall of the abdomen ; the caudal vein lies between the gland and the 

 ventral wall of the pelvis. They both join the external pudendal vein 

 which enters the abdomen by the inguinal canal. 



Blood is brought to the mammary gland by the external pudendal 

 artery, the main stem of which leaves the inguinal canal by the 

 subcutaneous ring and almost immediately divides into cranial and 

 caudal branches. 



Numerous nerves supply the mamma, and are derived from the ilio- 

 hypogastric, ilio-inguinal and genito-femoral (external spermatic) 

 nerves and from the caudal (posterior) mesenteric plexus of the 

 sympathetic. 



A small group of lymph glands — the superficial inguinal (lympho- 

 glandulse inguinales superficiales) — are associated with the external 

 pudendal artery and its cranial branch. 



Dissection. — Renaove the mammary glands and clean away the 

 surrounding fat. Then proceed with the dissection as in the male. 



If the subject is a male, the external genital organs must be 

 dissected before the wall of the abdomen itself is examined. 



External genital parts (Partes genitales externse). — The male 



external genital parts consist of the scrotum, the penis and the prepuce. 



The scrotum ^ is a membranous bag with a double cavity in which 



the testes are lodged. It lies in the pubic region between the thighs, 



and presents a slightly constricted neck where it is joined to the body 



wall. A shallow groove runs in a cranio-caudal direction (seldom 



exactly in the middle line), and in it there is an indistinct raphe^ scroti. 



^ Scrotum [L.], a bag. 



2 pa4>7i (raphe) [dr.], a seam. 



