. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CEPHALOPODA. 540 which they perforate, but there are no columns prolonged backwards from the lateral parts of the brain to form pal Hal ganglia as in the higher Cephalopods; the structure and func- tions of the cloak to which these ganglia are subservient, not being enjoyed by the shell- clad Nautilus. The nerves corresponding to the large visceral nerves of the Dibranchiates are, however, proportionally developed; for in the organs of plastic life the Nautilus is upon an equality with its naked congeners. These nerves,
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CEPHALOPODA. 540 which they perforate, but there are no columns prolonged backwards from the lateral parts of the brain to form pal Hal ganglia as in the higher Cephalopods; the structure and func- tions of the cloak to which these ganglia are subservient, not being enjoyed by the shell- clad Nautilus. The nerves corresponding to the large visceral nerves of the Dibranchiates are, however, proportionally developed; for in the organs of plastic life the Nautilus is upon an equality with its naked congeners. These nerves, which combine the functions of the sympathetic and par vagum, consist of a large pair derived from the lower part of the pos- terior cesophageal collar, and extending back- wards on each side of the vena cava; and of smaller twigs (17) coming off between the origins of the preceding nerves, and forming a plexus upon the parietes of the vein. The larger chords swell into ganglions at the termi- nation of the vena cava, (16, 16,) and send off ramifications to the branchiae, (15, 15,) the contents of the pericardium, and the viscera of digestion and generation. In the Dibranchiate Cephalopods which possess instruments for varied and active loco- motion, where the visual organ is of large size, and attains a complexity of structure equal to that of the Vertebrate animals, where a distinct acoustic organ is developed, and where the whole surface of the body is the seat of sensi- Fig. Nervous system of the Cuttle-fish. bility, the centre of nervous iinpression and volition is proportionally developed, and exhi- bits the highest conditions which the brain pre- sents in the Invertebrate series of animals. Except in some of the smaller species, as the Sepiola, in which the surrounding sub- stance still retains the consistency of a mem- brane, the brain, together with the anterior and posterior oasophageal collars, is entirely surrounded by a thick cartilage. The portion of oesoph
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