Nerves — Brain 



35 



v~. 



{yentr'ictilar gangUoti) which lies on the crop, and 

 gives off branched nerves to that organ and to the 

 gizzard. On either side of the recurrent nerve, just 

 behind the brain, are two nerve centres {paired 

 ganglia), one behind the other. They are connected 

 together by cords, also with the recurrent nerve, and 

 with the brain; 



they give off /^^^^S^^'^ ocx^ V'^ 



nerves to the /\ ^"^^'^^-^^^ A f^^ Ji " 



spittle -glands / v M '■'--5 



(fig. 26) (I). 



Brain. — It 

 has been men- 

 tioned that in 

 the nerve- 

 centres we 

 find, generally 

 speaking, 

 bundles of 

 fibres sur- 

 rounded by 

 layers of 

 nerve - cells. 

 In the brain 

 the arrange- 

 ment of the 

 various parts is 

 highly compli- 

 cated. The 

 brain of an 

 insect is regarded as made up by the fusion of 

 three pairs of nerve - centres. The foremost of 

 these comprises by far the larger portion of the 

 brain. Within the cellular envelope of the Cock- 

 roach's brain can be distinguished, on either side, 

 a basal mass of fibres {trabecula) whence arise two 



-OCuC 



IC3C 



Fig. 27. — Lobes of Cockroach's brain. A. Inner view ; 

 D. front view; C side view. c. cauliculus ; /. ped- 

 uncle ; t. trabecula ; ocx. outer and icx. inner brain- 

 cap. From Miall & Denny (after Newton). 



