AND PHYSIOLOGY. 



239 



both sides of the last caudal vertebra a pulsating organ which 

 receives the blood from the delicate veins of the caudal fin, 

 and propels it into the caudal vein, this constituting a true 

 caudal heart. 



425. Fishes' Blood.— The blood of 

 fishes, almost without exception, is of a 

 red color, and contains oval and slightly 

 bi-convex corpuscles. In one family 

 they are distinguished by their great 

 size, and thus resemble those of frogs ; 

 but other families have smaller ones. 



Fi(i. 241. 

 Smaller Circulation. 



Fig. 240. 



Blood Corpuscles of tf, 

 Lamprey Eel ; &, Skate. 



Branchio-Cardiac 

 Canals. 



Heart. 



Arteries. 



Greater Circulation. 

 Diagram of the Circulation in Fishes. 



426. Dorsal Vessel, or Heart of Articulates. — In ar- 

 ticulata, a vessel or tube passes along the back of the body — 

 behind the intestines and in front of the chain of ganglia — 

 called the Dorsal Vessel, which is divided into as many por- 

 tions as there are segments of the body. This is really the 



What peculiarity in the tail of the eel ? 4"5. What is the color of fishes' blood, and 

 what are its corpsucles? 426. What is the Dorsal Vessel of articulates? 



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