The brain as an organ of mind . sensory por-tion of each single ordouble ganglionthroughout the bodyof the Insect. It canprobably also transmitmotor stimuli alongother commissuralfibres to each motordivision of the samebody ganglia. In the Grasshopperthe brain is not three or fourtimes as large as one of the compound gan- ^^^^ system of the Great Greenglia in communication Grasshopper (Newport). A, brain ; B, optic nerves;D, antisnnal nerves ; d, motor nerve of mandiblefrom sub-oesopbageal ganglion ; [/, first thoracic gan-glion, connected to the second, as the second is
The brain as an organ of mind . sensory por-tion of each single ordouble ganglionthroughout the bodyof the Insect. It canprobably also transmitmotor stimuli alongother commissuralfibres to each motordivision of the samebody ganglia. In the Grasshopperthe brain is not three or fourtimes as large as one of the compound gan- ^^^^ system of the Great Greenglia in communication Grasshopper (Newport). A, brain ; B, optic nerves;D, antisnnal nerves ; d, motor nerve of mandiblefrom sub-oesopbageal ganglion ; [/, first thoracic gan-glion, connected to the second, as the second is to*^ * , the third, by two commissures. In Vertebrate Ani- with thewinffs. legs and 52 THE STRUCTURE OF mals we have a still farther concentration of the nervoussystem. In lower terms of the series, such as Fishesand Amphibia (fig. 56), this concentration is seen to themost marked extent in the chain of ganglia pertainingto the thorax and abdomen. In these animals and inall other vertebrates they are most completely fused into. uikn U! Fig. 19.—Transverse section through Iliiman Spinal Cord in cervical region,showing the organ to he composed of two symmetrical halves. (Sappey after Stilling.)The black portions orrespoud to regions containing longitudinal fibres ; the lighterportions represent the central Grey Matter and the horizontal roots of nerves;5, 6, commissu es connecting the symmetrical halves of the grey matter ; 11, 11,11 antcri ror motor roots of spii al nerves, coming from anterior Horns or Cornuaof Grey Matter, in which are mnnt-rous groiiiw of large ganglion cells; LS, pos-terior or sens. )ry roots of spinal nerves, entering the posterior Horns of Grey about eight diameters. a more or less cylindrical column known as the spinalcord. This cord constitutes a double and fused seriesof nerve centres in relation with the superficial as well aswith the deeper structures of the greater part of the body,including all the great nerves of the limbs. Chap.
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