METHODS OF RECONSTRUCTION. 359 



organs which it is intended to reconstruct is cut out as may be desired. Our bit 

 of wax then represents a model of the parts selected from the section, and equally 

 magnified in the three dimensions of space. Wax plates made from successive 

 sections are then piled up, one on top of the other, in the proper order,. If 

 they are rightly superimposed, an operation which often requires skill and judg- 

 ment, and always requires the utmost care, then the pile of plates will cor- 

 rectly represent the form of the parts included in the reconstruction. To fasten 

 the plates together it is only necessary to pass a warm metal instrument over the 

 edges of the plates, enough to melt the wax a little. With proper care this may 

 readily be accomplished without destroying the surface modelling of the recon- 

 struction. 



The simplest method of making wax plates is to have a large tin pan with 

 vertical sides. This is filled with hot water and melted beeswax is poured on the 

 surface of the water and allowed to cool. Plates of sufficiently exact and even 

 thickness may be cast in this way, provided the operation is carried out in a quiet 

 place so that the surface of the water is not disturbed while the wax is hardening. 

 It will be found convenient to have a large plate of iron, not less than \ of an 

 inch in thickness, which may be placed upon supporters. The tin pan should be 

 set upon this plate and the plate heated by lamps below in order to keep the 

 water hot enough to allow the wax to spread evenly over the surface of the water. 

 The water must be freed from air before the wax is poured in, but must not be 

 allowed to boil after the wax has been added. If bubbles appear in the wax 

 plate, they may be removed while the wax is still hot by directing the blue flame 

 from a Bunsen burner down upon them. If the pan is" heated directly without 

 the iron plate, it is sure to warp and become unfit for use. Thin iron plates are 

 also liable to be warped. 



To determine the thickness of the plates cast as described we proceed em- 

 pirically. A weighed quantity of wax is melted and poured into the pan. After 

 the plate has solidified it is removed by cutting it free from the edges of the pan, 

 and the thickness of the plate is then measured at various points by micrometer 

 callipers. From these data it is easy to calculate exactly what thickness of plate 

 one gram of beeswax represents. To get accurate results it is advisable to cast 

 several plates of varying thickness and determine the average for one gram in 

 that way. Having determined what one gram represents in thickness, it be- 

 comes thereafter only necessary to weigh out the proper number of grams in 

 order to obtain any desired thickness of wax plate. It will be found advantage- 

 ous to filter the wax before using it. This may easily be done by a double hot- 

 water filter. Such a filter may be made of copper. It is desirable to connect 

 it with a Mariotti's flask to maintain a constant water level. 



