134 



GENERAL PRINCIPLES OF ZOOLOGY. 



between the organs of respiration and of circulation. The 

 correlation finds expression in the fact that a double capil- 



FIG. 62. Schema of the course of circulation in a fish, a 1 , ascending aorta with the gill- 

 arteries (ka) ; 2 , the descending aorta formed by the union of the gill-veins (?<) ; kc, gill- 

 capillaries ; /;, auricle of the heart ; X-, ventricle ; vj, vena jugularis ; vc, vena cardinalis ; 

 vA, vena hepatica (inferior cava) ; da, intestinal arteries; dv, inttstinal veins ; sc, capil- 

 laries of the body ; Ic, liver-capillaries. 



lary region must be distinguished ; besides the body 

 capillary system already mentioned there is the respiratory 

 capillary region, whose exclusive office is to remove the 

 carbonic acid from the blood and to furnish oxygen to it 

 (gill and lung capillaries). A twofold capillary region 



