44 



Arterial System. 



The arterial blood in Eledone, as in Octopus, is 

 wholly enclosed in definite vessels. These have muscular 

 walls, which are consequently stronger and thicker than 

 the membranous walls of the veins. The pressure of the 

 blood in the arteries is very great indeed, but is slight in 

 the veins (Fredericq). As mentioned previously, the 

 arteries of Eledone radiate from three main trunks: — 

 (1) Anterior aorta, carrying blood to the cephalopedal 

 mass, the mantle and anterior portion of the alimentary 

 canal; (2) abdominal aorta, carrying blood to the 

 intestine and ink sac; and (3) genital artery, running 

 direct to the genital gland. 



The anterior aorta is a large vessel which, leaving 

 the heart, runs forwards, and curving round the liver 

 runs dorsal to this organ, and then lying to the right of 

 the stomach follows its outline for a time. Then, entering 

 the large venous sinus surrounding the oesophagus, it 

 runs alongside and to the right of the latter almost as far 

 as the cranial cartilage (fig. 42, Ant. A.). Soon after its 

 origin, the anterior aorta gives off a large branch which 

 immediately bifurcates into the right and left pallial 

 arteries (fig. 42, L. Pall. A.). The right vessel curves 

 round dorsal to the aorta, and then runs internal to the 

 visceral envelope, towards the funnel retractor. Just 

 interior to this it gives off a vessel which runs up 

 anteriorly, on the inner side of the visceral envelope, 

 giving off several small branches during its course 

 (fig. 42, V^E^A^). This artery, after furnishing several 

 small branches to the retractor infundibuli, ends in the 

 base of the funnel. The main pallial vessel now runs 

 below the posterior part of this funnel retractor muscle, 

 and so gains the inner face of the ventral part of the 

 mantle, and then runs obliquely to the stellate ganglion 



