. Animal physiology. Physiology, Comparative. NERVOUS SYSTEM OF MOLLUSKS. 353. guard the mouth; and they evidently correspond, both in position and functions, to the sensory ganglia of higher ani- mals, whilst the posterior gan- glion has for its office to regulate the respiratory movements. In the Pecten, however, as in other Conehifera which possess a foot (fig. Q'2), we find an addi- tional ganglion (c), the pedal, connected with the cephalic ganglia, and sending nerve- trunks to that organ. There is good reason to believe that, whilst the cephalic ganglia alone are the instruments oisensat
. Animal physiology. Physiology, Comparative. NERVOUS SYSTEM OF MOLLUSKS. 353. guard the mouth; and they evidently correspond, both in position and functions, to the sensory ganglia of higher ani- mals, whilst the posterior gan- glion has for its office to regulate the respiratory movements. In the Pecten, however, as in other Conehifera which possess a foot (fig. Q'2), we find an addi- tional ganglion (c), the pedal, connected with the cephalic ganglia, and sending nerve- trunks to that organ. There is good reason to believe that, whilst the cephalic ganglia alone are the instruments oisensatmi, so that they exert a general control and direction over the Fig. System of Pectek. movements of the animal, the a a, cephalic ganglia ; B, branchial pedal and branchial ganglia ganglion; C, pedal ganglion; .. ceso- minister to the reflex actions (§ 433) of the organs which they supply. 438. A similar arrangement is found in the higher Mollusks, among which the gangUa are more numerous, in accordance with the greater variety of functions to be performed. Of this we have an example in the Aplysia, a sort of sea-slug somewhat resembling those formerly alluded to (§ 316). In proportion as we ascend the scale, we find the cephalic ganglia rising higher and higher on the sides of the oesophagus ; and in the Aplysia they meet on the central line above it, forming the single mass (a, fig. 183), which receives the nerves of the eyes, tentacula, &c., and sends branches of communication to the other ganglia. The branches which it sends backwards are three on each A A. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carpenter, William Benjamin, 1813-1885. London : H. G. Bohn
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