41 6 MODELS FROM SERIAL SECTIONS [Ch. XI 



If a quotient is a mixed number reduce it to a fraction. The 

 numerator represents the number of sheets required and the denomi- 

 nator the number of sections to go with the sheets. 



Examples: (a) With a series of lo/x sections to be modeled at loo 

 enlargement each section of the series must be represented in the 

 model by a thickness of lo/i x loo = looo/i or i millimeter. If one 

 uses miUimeter or loooju paper, then looo/x -f- looo/i = y, and one 

 must use i sheet for i section. 



(b) With a series of lofx sections to be made into a model loo times 

 enlarged, and with blotting paper of i% mm. or goofi thickness, each 

 section must be represented by lojj, x loo = looo^u. If the blotting 

 paper is goojit thick, then it requires for each section: looo -r- 900 = i^ 

 sheets of paper or ^ sheets for one section or 10 sheets for 9 sections, 

 that is a double sheet for one of the nine sections. 



(c) With a series cut is;n, for a 50 fold model, each section is 

 represented by a thickness of 15/^ x 50 = 7So/x. If one uses i mm. 

 or looojLi blotting paper, then each section requires 750 -4- looo/x = f 

 of a sheet for one or 3 sheets for four sections. In this case one 

 omits every fourth section in drawing, thus: ist, 2d, and 3d sections 

 would be drawn; then the sth, 6th and 7th; 9th, loth, nth, etc., 

 every fourth being omitted. 



(d) If for the model just considered one had ^^ mm. or 900/x paper 

 then 750 -i- 900 = f . That is there must be 5 sheets of the paper for 

 each 6 sections. In that case every sixth section would be omitted 

 in the drawing, as every fourth section was omitted in (c). 



It is of course best to use sheets of exactly the right thickness to 

 represent the necessary thickness in the model (a), but one can pro- 

 duce models with accuracy by duphcating one or more sheets for 

 a group of sections (b) or by omitting certain sections of the series 

 in drawing (c, d). 



Drawings for Models 



§ 672. — The methods given for drawing microscopic preparations 

 in Ch. VI are all applicable except the freehand method. This is not 

 apphcable, because it is not possible to draw at a uniform and accurate 

 enlargement in that way. But the camera lucida method (§ 275) 



