156 E. T. NEWTON ON PREPARING A 



In No. 4 we find that while the parts noticed in No. 2 remain 

 much the same, two dark masses (mb) have appeared in the upper 

 portion, close to the mass (a), but definitely separated from it. 



In No. 6 the dark masses have increased in size and become 

 somewhat curved, but the most obvious difference is that the mass 

 (a) has suddenly extended inwards and downwards to the middle 

 line of the brain (in). 



In No. 10 the dark masses are much more deeply curved, the 

 upper portion of the mass (a) is rather less, and another process has 

 begun to extend upwards and outwards (st). 



In No. 13 the most important point to notice is that, while the 

 inner mass (a) has almost disappeared, the outer one (st) has 

 extended upwards, and may be seen to join the outer dark mass. 



In the 14th section the outer mass (st) joins the inner dark mass 

 also, and this junction extends as far as the 18th or 19th section. 



In No. 17 the outer mass (st) may be seen joining both the dark 

 masses, which are here very deeply hollowed out. 



In No. 120 the outer mass has entirely disappeared, and we have 

 simply a small portion of the lower mass (?n) left close to the middle 

 line, the dark masses are somewhat smaller. The extension (coin) 

 seen just below the antennary lobe is the commencement of the com- 

 missure to the lower division of the brain. 



In the sections which follow, all the parts above-mentioned, 

 excepting the commissure (com), get gradually less, and the dark 

 ones are seen, for the last time, in section No. 25. The median 

 portion (in), however, may be traced to the 28th section. 



The next step in the process was this : It occurred to me that, if 

 the card, upon which these outlines were made, were of a thickness 

 proportionate to the enlargement of the drawings, and if each were 

 cut out, and the whole piled together, one ought to have a model of 

 the exterior of the brain. I set to work, therefore, to do this, but 

 in order to lessen the labour as much as possible, it being merely an 

 experiment, it seemed desirable to make one half first, and instead of 

 making models of the whole series, the thickness of each slice was 

 doubled, so that it was only necessary to make 17, taking, as a 

 pattern, every alternate drawing. 



The material used was soft pine-wood, each piece being about the 

 ith of an inch in ftiickness. Having cut out each model slice with 



o 



a fine saw, the whole were piled together in their relative places and 

 temporarily fixed, so that the corners might be trimmed off, and the 

 result was the form which is seen in the model of one-half of the 



