NEGATIVE MAKING 83 



detail the making of each of the four nega- 

 tives reproduced in Figs. 19, 20, 21, 22, to 

 complete my remarks on bacterial photo- 

 micrography. 



Bacillus tuberculosis in sputum. Fig. 19. 

 Objective, Bausch and Lomb's iV oil immer- 

 sion, student's series; ocular, No. 4 Huy- 

 ghenian, of the same make; condenser, Abbe 

 chromatic, also of same series; radiant, acety- 

 lene,!^ foot burner; plate, Carbutt orthochro- 

 matic, 23 ; screen, yellow glass ; exposure, 7 

 minutes ; developer, eiko-hydro ; amplification, 

 1,000 diameters. 



Bacillus anthracis, spores. Fig. 20. Objec- 

 tive, Spencer's iV horn, immersion, student's 

 series; ocular, aplanatic i inch; condenser, 

 Ross' -TO achromatic, full cone ; radiant, acety- 

 lene, A foot burner ; plate, Forbes' orthochro- 

 matic S ; screens two, picric acid and napthol 

 yellow; exposure 3 minutes, less than half that 

 required for previous one (Fig. 19), due to 

 greater sensitiveness of plate, better lighting 

 by an achromatic condenser and the aplanatic 

 ocular ; developer the same, eiko-hydro ; ampli- 

 fication, 1,000 diameters. 



Streptococcus pyogenes. Fig. 21. Objective, 

 Powell and Leland iV horn, apochromat N. A. 

 1.40; ocular, condenser, plate and screens same 



