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This diagram shows the longitudinal section of the anterior end of the annelid. A, sagittal section; B, frontal section to show anterior portion of nervous system. b, brain; co., nervous collar about the mouth; c.v., contractile blood vessels; d, dissepiment; d.m., dermo-muscular wall; d.v., dorsal blood vessel; m, mouth; n.c., nerve cells; n.f., nerve fibers; np., nephridia; p, prostomium; ph., pharynx; s, setae; sn., segmental nerves; v.g, ventral chain of fanglia; v.v., ventral blood vessel. Only a portion of the blood vascular system is shown, and this appears unsectioned in the figure.

Annelid

This diagram shows the longitudinal section of the anterior end of the annelid. A, sagittal section;…

Nerve fibers. Labels: a, nerve-fiber, showing complete interruption of the white substance; b, another nerve fiber with nucleus. In both these nerve fibers the white substance is stained black with osmic acid, and the axon is seen running as an uninterrupted strand through the center of the fiber. c, ordinary nerve fiber unstained; d, e, smaller nerve fiber; f, varicose nerve fiber; g, non-medullated nerve fibers.

Nerve Fibers

Nerve fibers. Labels: a, nerve-fiber, showing complete interruption of the white substance; b, another…

This cut represents a portion of nerve, showing the filaments of which it is composed, and one of them drawn out.

Nerve Portion

This cut represents a portion of nerve, showing the filaments of which it is composed, and one of them…

Portion of the trunk of a nerve dividing into two branches.

Nerve Trunk Dividing

Portion of the trunk of a nerve dividing into two branches.

Nervous fibers, deprived of their neurilema and unraveled, showing the smaller threads, or filaments, of which the fibers consist.

Nervous Fibers

Nervous fibers, deprived of their neurilema and unraveled, showing the smaller threads, or filaments,…

Ultimate fibers of nerve highly magnified; showing the strings of globules of which they consist.

Nervous Fibers

Ultimate fibers of nerve highly magnified; showing the strings of globules of which they consist.

The spinal marrow. Labels: a, Spinal marrow. b, Fibers of sensation. c, Fibers of motion. e, Nerve.

Spinal Marrow

The spinal marrow. Labels: a, Spinal marrow. b, Fibers of sensation. c, Fibers of motion. e, Nerve.

Diagram showing relation of neurons composing the spinal nerve roots with adjacent nervous structures. Labels: S.E., sensory epithelium connected by a sensory neuron with spinal cord; S.M., striated muscle receiving the axon from a motor-cell in the ventral horn of the gray matter in the cord; Sp. F., spinal fibers, medullated, sensory, and the motor, passing to the sympathetic ganglion where they connect with sympathetic neurons; S.F., S.F., non-medullated fibers from the sympathetic neurons passing to the viscera, the axons going to the plain muscle (P.M.), the dendrites to the sensory endings (S.E.).

Spinal Nerve Roots

Diagram showing relation of neurons composing the spinal nerve roots with adjacent nervous structures.…