DISSECTED MODEL OF AN INSECT S BRAIN. 



157 



upper brain (Fig. 4). The different slices, however, were not left 

 fixed together, but were separated and arranged so that they might 

 be taken to pieces, as in the process of cutting sections, and the 

 surfaces thus exposed were coloured to represent the sections as they 

 appear under the microscope. 



an- 



Oj} 



CV-- 



111 - — 



conv- 



—c 



—-71lt 



—§b 



coin 



FIG. 4. — View from the outer side of the left half of model of upper 

 part of brain of Cockroach. The oblique lines in this and Fig. 5 indicate 

 the successive slices of which each is composed. Op, cut end of optic nerve ; 

 an, cut end of antennary nerve. 



FIG. 5. — Eight-half of model -brain seen from the inner side, with the parts 

 dissected away, so as to show, the anterior nervous mass, a ; the median 

 mass, m ; the mushroom-bodies, nib; and their stems (st). The cellular 

 cap, c, has been raised, so as to display the parts below ; com, is a part 

 of the commissure to the lower portion of brain, or infra-oesophageal 

 ganglia. 



This method of modelling was capable of still further develop- 

 ment. Having modelled the opposite half of the brain upon the 

 same plan, I drew upon each of the model sections, thus produced, 

 the outlines of the more important parts, as shown in the diagrams 

 (Fig. 3), and these were then cut out in the same manner as a 

 child's dissected map-puzzle. Now it will be obvious that by taking 

 from each of these " dissected " sections, the part, for instance, 

 which is in the diagrams (Fig. 3), marked (c), and joining them 

 together in their relative places, we shall have a model of that par- 

 ticular part ; and by joining, in like manner, the dark masses, and 



