Page:Illustrations of the comparative anatomy of the nervous system.djvu/31

 PLATE. IV.

VENTRAL ASPECT OF THE LOBSTER.

(ASTACUS MARINUS.)

THE greatest portion of the shell has been removed from the preparation from which this plate is taken. The nervous chord is seen about the first ganglion after the junction of the nerves passing on each side of the oesophagus from the brain, Branches are seen passing towards the mouth, and to the contiguous parts throughout the course of the chord; the nerves to be given to the legs are seen issuing from the ventral surface of the chord.

The posterior or dorsal layers of the nervous chord do not appear to send distinct fibrils to join the nerves issuing from the anterior or ventral; and the anterior do not send off branches forming distinct and separate ganglia, in the same manner as the posterior origins in most of the vertebrated animals; but the gangliform enlargements are concentrated in the chord.