CIRCULATORY SYSTEM. 583 



(1559.) In Sepia there is appended to each lateral heart a fleshy 

 appendage (m m), which, however, is not met with in the generality of 

 Dibranchiate Cephalopods. These bodies are attached to the hearts by 

 narrow pedicles ; and Professor Owen considers them to be rudiments of 

 the additional pair of branchiae met with in the Pearly Nautilus. 



(1560.) In Nautilus Pompilius the hearts just mentioned do not exist, 

 doubtless because the greater extent of surface afforded by the four 

 branchiae of this Cephalopod renders the presence of extraordinary 

 agents for impelling the blood through them, in order to ensure efficient 

 respiration, unnecessary. 



(1561.) After undergoing exposure to the surrounding medium in the 

 extensive ramifications of the branchial arteries, the purified blood is 

 returned to the organs belonging to the systemic circulation. In Sepia 

 it is first received from the branchiae by two dilated sinuses (ii), which 

 might almost be regarded as systemic auricles ; and from these it passes 

 into a strong muscular cavity (&), which corresponds in function with 

 the left ventricle of the human heart, and by its pulsations forcibly 

 propels the blood through all the arterial ramifications of the vascular 

 system. Two aortae, one derived from each of its extremities, arise 

 from the systemic ventricle, the commencement of each being guarded 

 by strong valves so disposed as to prevent all reflux towards this central 

 heart ; and thus the circuit of the blood, accomplished in this compli- 

 cated system of blood-vessels, is completed. In Nautilus the lateral 

 sinuses are wanting, and the systemic ventricle is of a square shape ; 

 but in other respects the course of the circulation is the same as is 

 above described. 



(1562.) In the Poulpe (Octopus vulgaris)*, the blood thus distri- 

 buted through all parts of the body by the arterial vessels returns 

 towards the branchiae through a system of venous canals composed 

 partly of vessels furnished with distinct parietes, partly of a series of 

 lacunae or spaces only circumscribed by the circumjacent parts. 



(1563.) The veins derived from the anus and the cephalic region, in 

 conjunction with those of the siphuncle and the great visceral veins, at 

 length unite and form by their union the two venae cavae (fig. 290, d d), 

 through the intervention of which the greater part of the blood is con- 

 ducted to the preliminary hearts (fig. 290, e e). So far these venous 

 trunks offer no very striking peculiarity, but arrived in the vicinity of 

 the gizzard they present a very remarkable arrangement : instead of 

 being formed by the junction of other smaller veins, they become un- 

 interruptedly continuous, with an immense venous reservoir which oc- 

 cupies all the dorsal aspect of the abdomen, and, indeed, they seem to be 

 a continuation of this membranous reservoir. It is to M. Delle Chiajef 



* Milne-Edwards, Ann. des Sci. Nat. 1845, torn. iii. p. 346. 



f Istituzioni di Anatomia e Fisiologia Comparata, pavte 1", Animali senza Ver- 

 tebre del Regno di Napoli, torn. i. 



