. Animal physiology. Physiology, Comparative; Physiology, Comparative. NERVOUS SYSTEM OF APLYSIA. 335. bling 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, 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 side. Of these, one passes through the ganglionic masses c c, to commu- nica
. Animal physiology. Physiology, Comparative; Physiology, Comparative. NERVOUS SYSTEM OF APLYSIA. 335. bling 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, 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 side. Of these, one passes through the ganglionic masses c c, to commu- nicate with the ganglion b, which is the one connected with the respiratory movements. The others are distri- buted with the branches of the ganglia c c, the function of which is double; for one set of branches from each is distributed to the mantle in general, every part of which (in these shell-less Molluscs) is capable of contracting and giving motion to the body; whilst another set is distributed to that thick and fleshy part of it which is called its foot, and on which the animal crawls (§. 120). There is another ganglion, d, lying in front of the cephalic ganglion, and also receiving branches of communication from it; this ganglion is specially connected with the actions of mastication and swallowing; and is called the pharyngeal ganglion. 439. Thus we see that the cephalic ganglion sends branches to all the other ganglia; though these, having different functions, do not communicate with each other : and every branch from the cephalic ganglia is distributed, with those of the ganglion it enters, to the organs supplied by the latter. Hence every part has two sets of nervous connections; one with the cephalic ganglia; and the other with its own ganglion. By the former, the animal becomes conscious of impressions made upon it, these impressions being converted in the cephalic ganglia into sensa- Fig. 172. -Nervous System of Aplysia,. Please note that these images are extracted
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