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Fro. 7 . The nervous system of the head of a grass- hopper, as seen by removal of the facial wall .4ntNv, antennal nerve; 1Br, gBr,3Br, the three parts of the brain; CoeCon, circumoesophageal connectives; 3Corn, suboesophageal commissure of the third Iobes of the brain; FrGng, frontal ganglion FrCon, frontal ganglion connective with the brain; LbNv, labial nerve; LraNv, labral nerve; MdNv mandibular nerve; MxNv, maxillary nerve; O, simple eye; OpL, optic lobe connected with the brain; RNv, recurrent nerve; 8oeGng, suboesophageal ganglion

lying against the lower wall of the first body seg- ment (Fig. 7, Gng ), which is likewise connect- ed with a fourth mass in the sec- ondsegment,and so on. The cen- tral nervous sys- tem of the insect thus consists of a series of small nerve masses united by double nerve cords. The nerve masses are known as gan- glia (Gng), and the uniting cords are called the connectives (Fig. 7, Con). Typi- cally there is a ganglion for each of the first eleven body seg- ments, besides the brain and the lower gan- glioia of the head.

The brain of an insect (Fig. 7 ) has a highly complex internal structure, but it is a less important controlling center than is the brain of a vertebrate animal. The other ganglia have much independence of function, each giving the stimuli for movements of its own segment. For this

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