CHAPTER VIII 



VISCERA 



N most snakes there is a very marked asymmetry 

 -*- of the viscera and their blood-supply, the organs 

 of the right side being anterior to, as well as larger 

 than, those of the left. 



The heart in most cases is situated between the 

 anterior seventh and the anterior fourth of the body ; 

 it may be much farther back, beyond the anterior 

 third, in Doliophis, Platurus, and some Viperidae and 

 Amblycephalidae, in the middle in Chersydrns. It is of 

 rather elongate form, enclosed in a pericardium in 

 which it lies freely, and has a sinus venosus, two 

 auricles, and a single ventricle divided by a septum. 

 Three arteries leave the ventricle, the pulmonary and 

 two systemic arches. The right systemic arch gives 

 off the carotid artery, which in many snakes, the 

 common Grass-snake for instance, may branch into 

 two, or in others be double from its origin. The 

 anterior abdominal vein is single in most snakes, 

 double in some Boidse, and conveys blood from the 

 ventral body-wall to the liver. The caudal vein is 

 continued as the renal portal. Veins which have 

 been regarded as remains of the two posterior cardinal 



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