Cff. X] PLOTTING PAPER MODELS 327 



made the Auzoux models molded from papier-mache such useful and 

 lasting additions to laboratory equipment ; and in the hands of Dr. 

 Dwight and Mr. Emerton, of Harvard University, have aided so 

 much in the demonstration of structure and form of special anatomic 

 preparations. " 



492. Thickness of Blotting Paper. Blotting paper of a 

 uniform thickness of i mm. f^mm. and y z mm. were found in the 

 market. The i mm. is known as 140 Ib. A. and costs about two 

 cents for a sheet 61 X 48 centimeters (24X 19 in.).* 



The thickness is easily tested by cutting out 50 small pieces, 

 piling them, dipping one end in melted paraffin and pressing them 

 together. The whole pile should of course measure 50 mm. if the 

 paper is millimeter paper. 



493. Size of the Model. In deciding upon the size of the 

 model to be made from a given series of sections one should select 

 the largest section and with the projection microscope throw the 

 image on the table (Fig. 258). By using different objectives and 

 different distances from the microscope one can find a size which 

 seems suitable. The magnification may be found by 207. Then 

 by multiplying the whole number of sections by the thickness of 

 the sections and this by the magnification one can get the length or 

 height of the model. One must take these preliminary steps and 

 decide upon the magnification to be used or the model is liable to 

 be too large to be manageable or too small to show well the neces- 

 sary detail. 



(i) Suppose the model is to be 100 times the size of the 

 original object, and the object has been cut into a series of sections 

 io/< thick. Then each section must be represented by a plate or 

 sheet 100 times as long, broad and thick as the object. As the 

 sheets of blotting paper are so large (61X48 cm.) one need be 

 solicitous only about the thickness. 



As each section is actually io// thick and the model is to be 100 

 times enlarged, the thickness representing each section must be 



*Book -stores, paper dealers and job printers are supplied by the paper 

 manufacturers with samples of blotting paper. One can look these samples 

 over, select and order the kinds desired. The millimeter blotting paper 

 mentioned in the text is one of the cheaper grades, costing by the package of 

 500 sheets about two cents a sheet (sheets 61 X48 centimeters, 24x19 inches). 



