Chapter XVII: Reconstruction of Objects from Sections 129 



by means of pins or fine nails. Remove all temporary wax 

 bridges (see 3) by means of a hot knife. 



When all blocks are properly adjusted and united, smoothe 

 over the surface by means of a hot spatula. 



MEMORANDA 



1. Geometrical Reconstructions, first described by Professor His, are 

 often all that is necessary to give one the desired information about 

 internal organs. Before sectioning, an outline drawing of the object is 

 made in a plane at right angles to the intended plane of section, and 

 under the same magnification that will be used for the reconstructed 

 drawing. For example, if the sections are to be transverse, the outline 

 drawing of the object would be a profile view from the side. After 

 sectioning the object, each section is drawn under the same magnification 

 as was used for the outline drawing. 



To reconstruct any special part of the object, draw a median line on 

 the outline drawing corresponding to the long axis of* the object. At 

 right angles to this line, draw a series of equidistant parallel lines 

 corresponding in positions to the sections that have been made. For 

 example, if the magnification is 100 diameters and the sections 10 microns 

 thick, then the parallel lines must be 1 mm. apart. Then, beginning 

 with the first section, indicate by dots in the proper plane in the profile 

 drawing the relative distances of the part in the sections above or below 

 the median line along the proper one of the parallel lines. All of the 

 sections having thus been plotted, connect the dots of corresponding 

 parts in the successive zones. It is frequently sufficient to reconstruct 

 only every fifth or even every tenth section. When the plane of section 

 is not quite at right angles to the axis of the object, an equal alteration 

 of angle must be made between the median line of the outline drawing 

 and the parallel lines. 



Such a reconstruction as the above would give lateral views of the 

 various internal parts. To get their aspects as seen from above or 

 below, the original outline drawing of the specimen as a whole should 

 have been made from this point of view instead of from the side. In 

 actual work one should make reconstructions in both planes. 



2. A Special Drawing-Table for rapid and convenient drawing of sections 

 for reconstruction has been devised by Bardeen. For details, see Johns 

 Hopkins Bulletin, XII, p. 148. 



