168 THE CRAYFISH. 



It then divides into two arteries, running forwards 

 and backwards respectively. 



a. The ventral thoracic artery runs forwards beneath 



the nerve -chain, supplying the sternal region of 

 the thorax, and the appendages from the hind- 

 most ambulatory legs to the mandibles. 



b. The ventral abdominal artery is a large median 



vessel given off by the sternal artery on reaching 

 the ventral region of the body. It runs back- 

 wards beneath the nerve-chain, and supplies the 

 ventral region of the abdomen and the abdominal 



The dorsal abdominal artery is a large median artery 

 arising from the ventral part of the hinder end of 

 the heart, and running backwards just above the 

 intestine to the hinder end of the body, supplying 

 the intestine, muscles, and other parts of the dorsal 

 region of the abdomen. It communicates at its 

 hinder end with the ventral abdominal artery. 



