36 ANATOMY OF A CHELONIAN. 



c. The great pectoral muscle on each side ; flat, and 

 made up of two portions — an anterior, which 

 will be seen to have arisen from the plastron 

 opposite the pectoral arch, and a posterior 



, larger portion, which arose from the plastron 

 considerably farther back. Both parts con- 

 verge to their insertion on one of the tuberos- 

 ities of the humerus (65). 



d. On the pelvis, a fan-shaped muscle, the origin 

 of which from the plastron has been divided in 

 removing the latter ; the anterior fibres (attra- 

 hens pelvis) run backward, the posterior (re- 

 trahens pelvis^ forward, to be attached to the 

 large process on the antero-lateral margin of 

 the pubis. This muscle is the homologue of 

 Xhe pyramidalis of human myology. 



e. On either side of the pectoral muscles, and 

 between them, portions of peritoneum are 

 seen, covered here and there (as is also the 

 ventral surface of the pericardium) with more 

 or less yellow fat ; in front of the pelvis the 

 anterior abdominal veins are very conspicuous, 

 lying on the peritoneum. 



79. Dissect away carefully the great pectoral muscles 

 and the pyramidales, noting the nerves which enter 

 their deep surfaces. Take care to avoid the branches 

 entering the anterior abdominal veins in front and be- 

 hind, and note : 



a. Through the pericardium and peritoneum, 

 the large quantities of lymph contained in the 

 cavities they enclose. 



b. On the peritoneum, the two Anterior Abdominal 



