32 ALLEN 



V.) ; or, if this vessel is absent, from one of the intestinal veins. 

 If desirable to fill the caudal, neural, and hcemal veins, a sepa- 

 rate injection of the caudal vein (fig. i, Cau.V.) is usually re- 

 quired. The entire arterial system can be filled from one of 

 \.h.Q gastric arteries (fig. i, L.Gas.A.), but an easier and more 

 satisfactory way, especially if the fish has no air-bladder, is to 

 make 2 injections of the dorsal aorta at a point marked X (fig. 

 i), shortly before it penetrates the kidney and posterior to the 

 origin of the coeliaco-mesenteric and subclavian arteries. A 

 cannula the proper size, having a rubber tube attached, was 

 slipped cephalad into the vessel and ligatured. If the aorta is 

 small, the rubber tube and cannula can be used as a blow pipe 

 to help open it up. The syringe is then filled with the Berlin 

 blue injecting mass ; as much air as possible is sucked out of 

 the tube and vessels before connecting the tube with the syringe ; 

 with a slow, steady movement, the mass is forced cephalad into 

 the aorta, from whence it passes into the carotids, efferent bran- 

 chial vessels, coeliaco-mesenteric and subclavian arteries, and 

 finally in like manner, from the same place, the aorta is in- 

 jected caudad, which fills the vessels of the kidney, reproduc- 

 tive organs, body wall, and tail. 



In tracing out the small peripheral vessels of the head, fins, 

 and viscera, I have found it very satisfactory to inject alone 

 the head, fins and viscera of a 15 to a 40 pound fish. The 

 head is severed dorsally several inches behind the skull, includ- 

 ing the pectoral and ventral fins, being careful not to cut or 

 injure any of the visceral organs. A ventral slit is then made 

 through the entire ventral wall to the vent ; the intestine is cut 

 at the rectum, and the entire viscera pulled out with the head. 

 In this manner the fish is cleaned, spoiling very little if any of 

 the flesh, after which the 2 cut ends of the cardinals (PI. I, fig. 

 I, L. & R.Car.V.), and the posterior end of the ventral artery 

 (PI. II, fig. 12, Ven.A.), if cut, were ligatured. Two injec- 

 tions, as described in the previous paragraph, were made ; one 

 from the hepatic vein, and the other cephalad from the cut end 

 of the dorsal aorta. 



In most cases it is best to make the dissections while the 

 material is fresh. As a preserving fluid I find nothing better 

 than formalin : it does not extract colors as does alcohol, and 



