192 



THE FROG— THE PLAT ANA 



Cut through the latter portion close to the arm, and fold it 

 backwards to expose the underlying brachial vein, 

 (ii) Two recti abdomini muscles, one along each side of the mid- 

 ventral Une of the body, and there separated by the white 

 line (linea alba). Each rectus abdominis muscle is trans- 

 versely divided into bellies. 



(iii) The deltoid muscle to the arm. 



(iv) The mylo-hyoid muscle, on the underside of the mouth region. 

 (v) The obliquus-externus muscles (which cover the sides of the 

 body) underlying the recti abdomini and the abdominal 

 portions of the pectoralis muscles. 



(b) The musciilo-cutaneous vein, lying Tinder the pectoralis muscle. It 



joins with the brachial to form the subclavian vein ; and it is formed 

 by branches from the skin and muscles in the region of the arm. [In 

 the Platana ihe muscular and cutaneous veins do not join to form one. 

 There is a second cutaneous vein arising from the shin of the abdomen 

 and joining the abdominal vein. Two small cutaneous veins are seen on 

 the skin of the leg, and another on the skin under the lower jaw. ] 



(c) The abdominal vein, visible through the body-wall as a dark longi- 



tudinal line between the recti abdomini muscles. Before it enters 

 the liver, it receives the hepatic portal vein from the gut and 

 spleen. 

 {d) The brachial vein of the arm. Near it is the white brachial nerve, which 

 may often be seen. Try to trace the point of junction of the brachial 

 and musculo-cutaneous veins, or the brachial, muscular, and cutaneous 

 veins in the Platana, as shown in the figures. 



Mylo-hyold muicle 



Bncfatal velnj 

 Mu«culo-< 



Deftold (Kuicle 



Pectoralii tnuacia' 



Cutincoi t vein] 



A B 



Fig. 66.— a. Muscular System and Vascular System (part) of Rana ; and B. of Xenopus. 



