. Elements of conchology / Prepared for the use of schools and colleges. Mollusks. NERVES OF MOLLUSKS, 13 pair of ganglionic swellings, which are lodged in a cartilaginous, cra- nial cravity; from them arise tbe nerves of the feet » (Fig. 5). To recapitulate, we see that, in this class of animals, ihe nervous sys- tem is -essentially comjwsed of a medullaiy collar, embracing the ali- mentary tube, and formed by the communicating cords of the tvt'o pairs of ganglia, which ai^ widely separated in the acephalous mol- lusks, but approx- imate more and more as we ascend in the series, form- ed by t
. Elements of conchology / Prepared for the use of schools and colleges. Mollusks. NERVES OF MOLLUSKS, 13 pair of ganglionic swellings, which are lodged in a cartilaginous, cra- nial cravity; from them arise tbe nerves of the feet » (Fig. 5). To recapitulate, we see that, in this class of animals, ihe nervous sys- tem is -essentially comjwsed of a medullaiy collar, embracing the ali- mentary tube, and formed by the communicating cords of the tvt'o pairs of ganglia, which ai^ widely separated in the acephalous mol- lusks, but approx- imate more and more as we ascend in the series, form- ed by the gaster-^ opods and cepha- lopods; and the. Fig. 5. NERVOUS SYSTKM OF T5IS OUTTSuE-FISH. Exphrmtion of Fig. 5.—Nervous system of the cuttle-fish ;—a. the ner- vous collar which embraces the cesophagus, the course of wliich is indi- cated by a bristle (s):—c, the nervous mass, situate in front oftheflesophagus, and commonly called the brain : the upper surface is surmountied by a very large cordiform tubercle, and from its anterior part arise two nerves that soon terminate in a circular ganglion, which, in its turn, gives rise to another pair of nerves, which descend beneath the mouth so as to embrace thecesophagus again, and then form a small anterior ganglion from which arise the labial nerves ;^-5. the tentacular ganglia, from v/hich arise the nerves of the arm;—o, tlie optic nerves which arise from the lateral parts of the brain, and soon s%vell into a large ganglion ;—t. small nervous tuber- cles, situate on the origin of the optie nerves;—g. the sub-oesophageal or ventral ganglion ;—r, the great nerve of the viscera, one branch of which presents asi elongated ganglion (r), and penetrates into the branchiae;—7ft nerves which also arise from the post-oesophageal ganglia, and which, in their course, present a large star-Ukc ganglion (e), the branches of wi^ch are distributed to the mantle. 2. Please note that these images are extracted from scanned page ima
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectmollusks, bookyear184
