212 



FISHES 



The gullet opens into the stomach, which consists of an 

 anterior region that extends straight back and ends blindly; 

 a posterior region that leaves the anterior region at right 

 angles near its middle; and three long, cylindrical, blind 

 sacs, the caeca (Fig. 148). The intestine begins just back 

 of the C£eca and after one or two turns terminates at the 

 anal opening. The liver lies in the anterior end of the body 

 cavity and has on its posterior surface a gall bladder which 

 empties its bile through a short duct into the anterior part 

 of the intestine. 



Circulatory system. — The heart of the perch lies between 

 the gills and is in close relation to them. It is inclosed in 



Eff^erdgiU arteries W epctMc art^ y^ 



CmdalarleTy 



CauddLveln 



'idneif 



Tf„i,rF 1' — ~. \ 'Mvm&ntarj/ canal 



neoTv UepaUcvem t,iver 'Mesenteric. artem 



Fig. 149. — • Circulation of a fish. 



the pericardi?! cavity which is entirely separate from the 

 main body cavity. The heart consists of three parts, the 

 sinus venosus, the thin-walled auricle, and the muscular 

 ventricle, placed in the order named, beginning at the 

 posterior end. The ventricle pumps the blood from its 

 anterior end through a large artery that sends a branch to 

 the lower end of each gill. The blood then flows upward 

 through the gill filaments and leaves them from the dorsal 

 ends through arteries that finally meet in the median plane 

 on the dorsal side of the body cavity and form the dorsal 



