RECONSTRUCTION BY MEANS OF WAX PLATES. 57 



aid of a camera lucida, or by means of a projection apparatus. Bardeen 

 has devised a drawing table which is placed horizontally, over which is 

 placed a mirror at an angle of 45 degrees. The table may be made to 

 move by means of a windlass toward or away from the microscope so 

 that any magnification may be quickly obtained. An ordinary micro- 

 scope with the tube placed horizontally may be used, the illumination 

 being obtained from an arc light. (For further details see Bardeen, 

 "Johns Hopkins Bulletin," vol. xii, p. 148.) Sharp outlines of the 

 parts to be reconstructed should be made and the drawing for each sec- 

 tion labelled with reference to the series of drawings and with reference 

 to the number of the section, as it is often necessary to refer to the sec- 

 tions while reconstructing. After the drawings have been completed 

 they are transferred to the wax plates, which is conveniently done by 

 placing the drawing over the wax plate and tracing the outline with a 

 blunt-pointed instrument, using some pressure while doing so. The wax 

 plates are numbered with reference to the drawings. It is necessary to 

 maintain an equal ratio between the diameter of the magnification of the 

 drawing of the sections, the thickness of the plates used and the thickness 

 of the sections. Thus, if it is desired to reconstruct portions of a series 

 of sections 5 /j. in thickness and to use wax plates 2 mm. thick, the draw- 

 ings need to be made at a magnification of 400 diameters. 



Cutting Out the Parts to be Reconstructed and Completing 

 the Model. Those portions of the wax plates representing the parts to 

 be reconstructed as outlined by the tracings are cut out with a sharp 

 knife with narrow blade, the wax plate being placed on a glass plate 

 during this procedure. If the parts of the sections to be reconstructed 

 consist of a number of disjointed pieces, these are retained in their rela- 

 tive positions by means of remaining bridges of wax, which should be 

 firm enough to keep all parts in their proper relation. The parts of each 

 wax plate representing the portions of the section to be reconstructed are 

 piled up in their proper sequence as they are cut out. The completion of 

 the model consists in accurately adjusting the portions obtained from each 

 wax plate to those which precede and follow them. This process is 

 facilitated by building up the model in blocks representing five sections, 

 as has been suggested by Bardeen. Those parts representing the portions 

 of the sections to be reconstructed are united together by pins or small 

 nails ; other parts, such as wax bridges, are removed by means of a hot 

 knife. The successive blocks are then similarly united and the model is 

 Completed by smoothing over the surfaces by means of a hot iron. 



