450 THE NERVOUS SYSTEM. 



fungiformia and their trabecula;, and the increase of the pro- 

 cerebral lobes, which I take to be the lateral lobes of the 

 middle protocerebron of Viallanes. This structure in the 

 higher Insecta, as in the Blow-fly, assumes a new import from 

 its remarkable connections and its cerebroid character. 



c. Details of the Structure of the Brain of the Blow-fly Imago. 



The brain of the imago of the Blow-fly, and under this term 

 I include all the cephalic nerve centres, agrees in structure 

 very closely with that of all the higher Insecta. It is formed 

 upon the same ground plan as that of the Arthropoda in 

 general. 



Size of the Brain as compared to the Body-weight. The propor- 

 tionate bulk of the brain in insects to that of the body has 

 been frequently estimated, and the following table, taken from 

 Graber [10], represents the results arrived at. The bulk of 

 the brain is : 



In Dytiscus 4 ^V o of that of the body. 



In Melolontha vulgaris :i 



In Ichneumon Sp. (?) 



In the Honey-bee - 



In the Ant .^l, t . 



In the Blow-fly I find it to be ., ,', 

 These numbers do not, however, fairly represent the propor- 

 tion owing to the large air-spaces of the body. I have en- 

 deavoured to determine the relation of the weight of the 

 I MM in as compared to that of the bod)- in the Blow-fly, and it 

 may be set down approximately at between .^ and ^ of the 

 body-weight. Taking the Bee and Wasp as standards of com- 

 parison, its proportionate weight is less than in these Hymenop- 

 tera, in which I should estimate it as between -j-^- and -^^ of 

 the body-weight. Cuvier gave an estimate of the proportion 

 of the weight of the brain to that of the body in several groups 

 of Mammals, and he found the weight of the brain in the 

 larger cnrnivora varied between ._.,', and . V( },-, of the body- 

 weight. In small birds it is about ten times greater, or from 



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