(a) The muscles:
(i) Two pectoralis muscles passing from the base of the arm, the one to the middle line of the body, and the other over the abdominal region to the posterior part of the body. Cut through this latter muscle at its anterior end, and fold it backwards to expose the underlying brachial vein.
(ii) The rectus-abdominis muscles passing along the mid-ventral line of the body, with the white line (linea alba) in the centre.
(iii) The deltoid muscle to the arm.
(iv) The mylo-hyoid muscle, on the underside of the mouth region.
(v) The obliquus-externus muscle, lying under the second pectoralis muscle noted above.
(b) The cutaneous and the muscular veins, lying under the pectoralis muscle, and arising independently from the subclavian vein. They supply the skin and muscles in the region of the arm. There is a second cutaneous vein arising from the abdominal vein and extending on to the skin of the abdomen. Two other small cutaneous veins are seen on the skin of the leg, and another on the skin under the mouth.
[In the Frog a single musculo-cutaneous vein is seen lying under the pectoralis muscle and extends on to the skin.]
(c) The abdominal vein, partly visible through the wall of the body, in the centre of the rectus-abdominis muscle.