510 



ZOOLOGY 



SECT.. 



heart are valves which allow of the flow of blood in one f^e* 

 only, viz. from the heart to the artery. From the anterior end 

 of the heart arise five vessels the median ophthalmic artery 

 (Fig. 401, oa.), which passes forwards to the eyes ; paired an- 

 tennary arteries (aa.\ going to the antennules, antenna, green 

 glands, &c., and sending off branches to the stomach ; and paired 



FIG. 403. Diagram of kidney of Astacus flu vi at ills. I, unravelled ; II, the parts in their 

 natural relations. II. bladder ; c. p. cortical portion ; d. duct; s. sacciili ; w. p. white 

 portion. (After Marchal.) 



hepatic arteries, going to the digestive glands. The posterior end 

 of the heart gives off two unpaired arteries practically united 

 at their origin, the dorsal abdominal artery (oaa.), which passes 

 backwards above the intestine, sending branches to it and to the 

 dorsal muscles ; and the large sternal artery (sa.), which passes 

 directly downwards, indifferently to right or left of the intestine, 

 passing between the connectives, uniting the third and fourth 



