THE LIZARD. 159 



XV. Cut through the origins of both pectoral muscles 

 and reflect them outwards : dissect ^.way the 

 external oblique and note 



129. The ribs and sternum, and their relation to the 

 body walls (see §§ 22-25 ^nd Fig. 39). 



130. The external intercostal muscles ((?./), filHng 

 up the interspaces between the ribs : their fibres run from 

 any given rib backwards and slightly downwards to its 

 successor. 



131. The obliquus internus (o.i), a thin sheet of 

 muscle lying between the intercostals externally and the 

 rectus ventralis internally, and exposed by the removal of 

 the external oblique : its fibres pass downwards and forwards. 



XVI. Make a longitudinal incision through the rectus 

 ventralis, a little to one side of the median line, 

 taking cave not to injure the epigastric vein 

 (§ 138): continue the incision backwards to the 

 pubes, and forwards by cutting through the 

 sternum and interclavicle : carefully separate the 

 epigastric vein from the surrounding tissues and 

 reflect the body walls. Note 



132. The coelome or body cavity, containing the viscera, 

 extending in front to about the level of the interclavicle, and 

 behind continued beyond the anterior boundary of the pubes 

 as the pelvic cavity. 



133. The peritoneum (parietal lay^r), a thin membrane 

 lining the coelome : in the posterior half of the cavity it is 

 deeply pigmented, in the anterior half colourless, the 

 boundary line between the black and colourless portions 

 being perfectly sharp. 



134. The liver (Fig. 40, /r), a large, brownish organ, 

 occupying about the middle third of the body cavity, and 

 imperfectly divided into right and left lobes. 



