. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. 9o PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. structure, no repetition of similar parts in a linear series. Now it is probable that the nervous system controls the general structure of the body. Thus while the nervous system of vertebrates is a continu- ous axis, and that of arthropods and worms a string of ganglia running through the body, in mollusks there is no axial arrangement as in verte- brates, nor a linear series of gan- glion as in arthropods. General Plan of the Nervous Sys-
. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. 9o PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. structure, no repetition of similar parts in a linear series. Now it is probable that the nervous system controls the general structure of the body. Thus while the nervous system of vertebrates is a continu- ous axis, and that of arthropods and worms a string of ganglia running through the body, in mollusks there is no axial arrangement as in verte- brates, nor a linear series of gan- glion as in arthropods. General Plan of the Nervous Sys- tem.—In these animals the nervous system consists (i) of an oesophageal collar, and (2) of ganglia irregular- ly placed wherever important func- tions, either nutritive or locomo- tive, are situated. Examples.—1. In bivalves (acephala), such as clams, for instance, we have (Fig. 63): (1) The oesophageal col- lar, which presides over the mouth and head functions (e. g., gathering of food and whatever beginnings of intelli- gence the creature may possess), and also has general presidence over conscious voluntary move- ments, and therefore over other ganglia; (2) a large visceral gan- glion in the region of nutritive and respiratory organs, to pre- side over these; and (3) a loco- ,.„. N| ..,, „ , motive or foot ganglion to con- an oyster : c, cephalic gan- trol locomotion. This is all. In glion; v} the visceral gan- . glion. the oyster the nervous system is Fig. 63.—Nervous system of a clam : eg, cephalic ganglion ; pg, pedal ganglion ; vg, visceral 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 LeConte, Joseph, 1823-1901. New York, D. Appleton and Company
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