MILLEE — CONTRIBUTIONS FROM ANATOMICAL LABORATORY. 211 



THE VASCULAR SYSTEM OF Necturus ma.cuUtus. 



THE ARTERIES. 



For convenience of description the ventral aorta and its 

 branches will be considered with the arteries although it con- 

 tains venous blood. 



From both sides of the anterior extremity of the Teuncus 

 Arteriosus, Tr. PI. 9, and fig. 1, PI. 10, arise two vessels, a 

 smaller anterior and a larger posterior. For a distance of about 

 5 mm they appear as a single vessel, being separated merely by 

 a septum. The anterior. The First Afferent Branchial 

 Artery, A. B.-l, PI. 9, and fig. 1, PL 10, runs out almost at 

 right angles to the truncus, to the first branchial cai'tilage, along 

 the postero-ventral edge of which it continues to the gill. In 

 the gill it runs along its ventral edge, giving rise to numerous 

 fine branches which subdivide and form a loop, with a capillary 

 network between, in each tuft. The posterior larger vessel also 

 runs out nearly at a right angle to the truncus parallel to the 

 first afferent vessel, then makes a sharp turn caudal, continuing 

 between the two posterior branchial cartilages. About 5 mm 

 posterior to the turn it divides into two branches, the Second 

 and Third x\fferent Branchial Arteries, A. B.-IL, A. B. 

 -III., PI. 9, and fig. 1, PI. 10. Each runs along the correspond- 

 ing branchial cartilage into the gill, where it breaks up in a man- 

 ner similar to the first. 



The Efferent Branchial Arteries arise by numerous radi- 

 cles formed by the capillaries of the gill tufts uniting along the 

 dorsal edge of the gill to form a common vessel. Just at the 

 point where the First and Second Efferent Branchial Ar- 



