SANGUIFEROUS SYSTEM 46/ 



formed by their union, and surrounding the head anterior to 

 the eyes and beneath the external muscular aponeurosis of 

 the connecting membrane of the arms. The interbrachial 

 veins are formed by the union of the two contiguous lateral 

 veins of each pair of arms, as seen in the octopus ; and the 

 two lateral portions of the circular cephalic vein uniting in 

 front, behind the syphon, to form the great anterior vena 

 cava, have each an internal semilunar valvular fold defending 

 the orifice leading into the cava. The trunk of the superior 

 cava continues its course downwards or backwards, on the 

 left side of the intestine, and exterior to the muscular apo- 

 neurosis embracing the liver, receiving venous branches from 

 the syphon, the fore part of the liver, and the muscular pa- 

 rietes of the mantle. After a short course along the front of 

 the liver the vena cava bifurcates, and its two branches proceed 

 laterally to the two divisions of the auricle placed at the base 

 of the branchiae. The muscular cavity of each of these auri- 

 cles is preceded by a perceptible sinus venosus, as in the 

 auricle of most fishes ; they have often a dark or blackish 

 colour, like the auricles of many conchifera, and in the naked 

 tentaculated species, erroneously designated decapoda, there is a 

 small hollow fleshy appendix communicating by a short tubular 

 cervix, with the cavity of each auricle. The exterior appendices 

 of the auricles are not found in loligopsis, octopus nor nautilus. 

 The trunk and bifurcation of the vena cava are covered 

 with saccular vesicles, cellular internally, which communi- 

 cate freely with the cavity of the veins, and are lodged 

 with them in the same two membranous thoracic venous 

 cavities. They form two bifid clusters on each side in the 

 nautilus as described by Chiaje. The wide membranous 

 cavities, containing these venous branches and vesicles, 

 communicate by two lateral tubular openings with the general 

 cavity of the mantle, and thereby with the exterior medium ; 

 and these cellular vesicles may thus be destined to secrete or 

 absorb some materials to affect the constitution of the blood. 

 Each lateral auricle, like the systemic ventricle, is here en- 

 closed in its distinct pericardium, and each sinus venosus 

 receives, besides the branch of the vena cava, a large lateral 

 palleal vein, returning the blood from the corresponding 

 side of the mantle and the suspensory ligament of the bran- 

 chiae. The venous blood is returned from the different 



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