454 DAVID H. DOLLED 



the square of the short diameters gave an expresson of the 

 relative volumes which may be proved mathematically to be 

 as exact as actual calculations of volume. The same lens system 

 was used throughout, Zeiss comp. oc. 8, 2 mm. oil immersion, 

 normal tube length, X 1960 at table level. 



2. The calculation for the individual cell from serial sections 



a. By wax reconstruction. Sections in serial were cut at two 

 and at one micra from two animals, Experiments Shock 37 and 

 Normal 19. The Minot precision microtome was employed. 

 The one micron sections were only obtained by lightly bevelling 

 an extremely sharp and microscopically smooth edge of the knife 

 in the fashion of a scissors blade. With sufficient perseverance 

 places were found which gave fairly perfect sections, free from 

 side to side compression and wrinkling. Dusting the knife 

 surface with talcum powder helped greatly to prevent wrinkling 

 and sticking. Fortunately with such an edge the sections ribbon 

 nicely. 



The knife set for two micra gave from seven to eleven sections 

 through individual resting cells and for one micron from sixteen 

 to twenty-three, which is only one of many confirmations of 

 accuracy on the mechanical side. 



The adjustment of the magnification to correspond to the thick- 

 ness of the wax plate was the step next in place and importance. 

 After making a plate of approximately the desired thickness, 

 its exact thickness was determined by the use of a micrometer 

 caliper reading accurately to hundredths and closely to thou- 

 sandths. Twelve readings were made at different places on the 

 plate and the average reading was used as the working figure. 

 No plate used gave an extreme of variation in the individual 

 readings of more than one-tenth of a millimeter. So great a 

 variation was very exceptional. The determination of the 

 magnification to suit was also made to depend upon the average 

 of numerous readings from the Zeiss object-micrometer. Various 

 combinations of lenses and tube length were necessary and all 

 projections were drawn at stage level. The majority of recon- 



