152 THE CRAYFISH 



4. The sternal artery is single, and arises from the hinder 

 end of the heart, whence it runs directly downwards, 

 passing to the right or left of the intestine, and 

 between the connectives uniting the fourth and fifth 

 ganghon-pairs of the thoracic nerve-chain (p. 148). 

 It then turns forwards beneath the nerve-chain, 

 supplying the sternal region of the thorax, and the 

 appendages from the hindmost ambulatory legs to 

 the mandibles. 

 a. 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 

 appendages. 



6. 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. 



