4 i2 MODELS FROM SERIAL SECTIONS [Cn. XI 



3. The sections must be drawn as much larger than the actual 

 specimen as the model is to be larger than the object. 



4. The drawings with the desired outlines must be made directly 

 upon or transferred to the sheets of modeling material which are then 

 cut out, following the lines of the drawing. 



5. The different plates of modeling material representing all the 

 sections are then piled up, in order, thus giving an enlarged model 

 of the object with all its parts in proper position and in true pro- 

 portions. 



MODELS OF WAX 



667. Wax models. For making wax models, beeswax 820 

 grams, paraffin 270 grams, and resin 25 grams are melted together 

 and thoroughly mixed. 



To get the sheets of wax of the proper thickness two methods are 

 available: 



(1) The hot wax is poured into a vessel containing hot water. 

 The wax spreads out into an even layer over the hot water and is 

 allowed to cool. While it is solidifying it should be cut free from 

 the edges of the vessel. Of course by calculation and experiment 

 one can put in the right amount of wax to get a plate of a given 

 thickness. 



(2) One must have a wax-plate machine consisting of a flat sur- 

 face planed cast iron is good with some means of obtaining 

 raised edges. If these are adjustable by a micrometer screw it is 

 simple to set them properly for the desired thickness of plate. Then 

 there must be a hot roller. The hot wax is poured on the plate, and 

 with the hot roller resting on the raised edges the wax is rolled out 

 into a plate. It cools quickly and may be removed for another plate. 

 This is the most rapid and satisfactory method of preparing the 

 plates. By using a brush with turpentine the paper with the draw- 

 ing can be wet and then with the hot roller cemented to the plate 

 before that has been removed from the machine. 



The wax plate is cut with a sharp instrument, following the outlines 

 of the object which has been traced upon it by the aid of a camera 

 lucida or the projection microscope. The sections are piled together, 

 some line or lines obtained from a drawing or photograph of the 



