The brain as an organ of mind . alf of the body of one of these ani-mals there is a complex aggregate of the mechanisms forreflex actions—represented by ingoing fibres entering asensory ganglion in connection with a motor ganglion,together with outgoing fibres issuing from the in addition, the two halves of the nervous systemare united to one another by the above-mentioned trans-verse commissures. It is by virtue of these connectionsbetween the respective ganglia of the two sides that aproperly co-ordinated activity of the whole body is renderedpossible, in response to sensory st
The brain as an organ of mind . alf of the body of one of these ani-mals there is a complex aggregate of the mechanisms forreflex actions—represented by ingoing fibres entering asensory ganglion in connection with a motor ganglion,together with outgoing fibres issuing from the in addition, the two halves of the nervous systemare united to one another by the above-mentioned trans-verse commissures. It is by virtue of these connectionsbetween the respective ganglia of the two sides that aproperly co-ordinated activity of the whole body is renderedpossible, in response to sensory stimuli. In other animals, such as the Grasshopper, whilst thebilateral symmetry of the nervous system (fig. 18) is justas obvious, it is much more complex and more developedlongitudinally. The sensory and motor ganglia are nume-rous and are arranged side by side in serial order, thoughmany of them are more completely fused with one anotherand with those of the opposite side than is the case with Chap. II.] A NERVOUS SYSTEM. 51. the two pairs of gan-glia of Eolis. Thusmedian compoundganglia (fig, 18, g)are formed, connectedwith one another bysingle, or it may beby double (<?, //) com-missures. The ter-minal double group(a) represents thebrain of the animal,and this is probablycapable of receivingstimuli by some fibresfrom the 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 ST
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