72 THE PHYSIOLOGY OF THE COMMON CRAYFISH. 



traverses the nervous cord (figs. 12 and 15), and divides 

 into an anterior (fig. 12, s<i) and a posterior [iaa) branch, 

 both of which run beneath and parallel with that cord. 



o.a-. 



h.a: 



sta- 



sa.ft. 



FxG 1(1. — Axfnois JfuriatiHs.— Theheavt ( X 4). A, from above ; B, from 

 below ; C, from the leftside, aa, antennary artery ; nc, alte cordis, 

 or fibrovis bands connecting the heart with the walls of the peri- 

 cardial sinus ; h, bulbous dilatation at the origin of the sternal 

 artery; 7;^. hepatic artery ; /.'/, lateral valvular apertures ; wf, oph- 

 thalmic artery ; s.a, superior valvular apertures ; .i.a.a, sx;perior 

 abdominal artery ; st.a, sternal artery, in B cut off close to its , 

 origin. W 



A third arter}' runs, from the front part of the heart, 

 forwards in the middle line, over the stomach, to the 

 eyes and fore part of the head (figs. 5, 12, and 16, oa) ; 

 and two others divercfe one on each side of this, and sweep 



