DISSECTION OF THE ABDOMEN. 287 



and is distributed to the sci'otum and prepuce (skin of mammary gland 

 in mare), superficial inguinal glands, and skin, terminating a little in 

 front of the umbilicus. 



The Subcutaneous Abdominal Vein runs in company with the artery. 



The Superficial Inguinal Lymphatic Glands (Plate 38). These 

 form a small group close to the subcutaneous abdominal artery, at the 

 side of the prepuce. 



The Subcutaneous Thoracic (Spur) Vein (Plate 38) will be found 

 on the surface of the panniculus. The primary rootlets of the vein 

 collect blood from the skin in front of the mamma or prepuce, and pass 

 on to the surface of the panniculus, where they unite to form the trunk 

 of the vein. This is at first lodged in a groove on the superficial aspect 

 of the paimiculus. It then perforates the muscle ; and gaining its deep 

 face, it passes forwards towards the axilla (Plate 1), where it joins the 

 brachial vein. The course of this vein is usually distinctly visible in the 

 living animal. From its position it is liable to be injured in deep 

 spurring, and hence one of its names. 



The Panniculus Carnosus (Plate 38). This is a thin extended sheet 

 of muscular tissue, which is adherent to the deep surface of the skin 

 over a large part of the abdomen and thorax, being continued also from 

 the latter region over the outer aspect of the shoulder. The most 

 posterior angle of the muscle is included in the fold of skin at the groin, 

 but it does not reach the hind limb. From this angle the superior edge 

 of the muscle (which will not at present be seen) slopes upwards with 

 two or three wide sinuosities to near the spine in the doi'sal region, 

 while from the same point the posterior edge of the muscle slopes down- 

 wards and forwards to a second angle which is rounded and placed from 

 three to six inches external to the umbilicus. The inferior edge extends 

 from this latter angle forwards towards the elbow. Anteriorly the 

 muscle is continued over the scapular region, and sends also an apon- 

 eurotic tendon between the fore limb and the chest-wall to be attached 

 to the internal tuberosity of the humerus. The edges of the muscle are 

 prolonged by a thin fascia which is attached superiorly to the vertebral 

 spines, and below and behind is adherent to the abdominal tunic. The 

 outer surface of the muscle is with difticulty separated from the skin, 

 which indeed receives the insertion of its fibres. The muscular tissue 

 of the panniculus is, as compared with striped muscles in general, of a 

 pale colour. 



Action. — It twitches the skin, and plays the part of a hand to the 

 animal in removing offending insects. 



Directions. — Begin at the lower edge of the panniculus and raise it 

 upwards from the subjacent structures. This is easy over the abdo- 

 minal tunic, but anteriorly it is closely adherent to the edge of the 

 deep pectoral muscle. The panniculus is not to be removed, but raised 



