240 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 47. 



The ground glass of the lamp is of a kind not to absorb much light, and 

 yet of a fine grain. The 5-candle lamp suffices for magnifications of 

 500 to 600 diameters ; the 10-candle for immersion systems. The 



electromotive force recommended 

 by the inventor is 105 volts. 



Glass-rod Substage.* — F. W. 

 Leggett has found that a glass 

 rod gives a fine illumination with 

 -} objective and No. 3 eye-piece. 

 The rod consists of Bohemian 

 glass i in. diameter, 3j in. long, 

 bent at an angle and polished at 

 both ends ; this is incased in 

 metal, the inner surface of which 

 is polished. Attached to the end 

 toward the light there is a funnel 

 3^ in. long, expanding from \ in. 

 to If in. in diameter and highly 

 polished in its interior. At the 

 end near the light is inserted an 

 ordinary bull's-eye lens, so placed 

 that the rays of light pass through 

 the rod to the object on the stage of the Microscope. Should the light 

 be too intense for low powers, it can be modified by removing the 

 bull's-eye condenser. 



(4) Photomicrography. 



Photomicrography. \ — D. W. Dennis, in the first of a series of 

 articles on this subject, gives in the following words his opinion regard- 

 ing the choice of apparatus. 



" One reason why photomicrography has not hitherto succeeded better 

 is that a cheap apparatus, scraped together from a microscopic and a 

 photographic outfit, has been recommended. This cheap apparatus was 

 always the most expensive to be had, for the reason that the time con- 

 sumed in getting ready for, and making, a successful exposure costs, in 

 the end, more than the investment for a correct outfit. In the second 

 place the results, for reasons above given, were never valuable except in 

 the case of slides so perfectly prepared that they had to be the best of 

 an expert microscopist's work. I, again and again, concluded, while 

 using these makeshifts, that histological slides could not be successfully 

 photographed. I thought photomicrography was an art, the usefulness 

 of which was confined to the resolving of lines on diatoms, and reproduc- 

 ing the silhouettes of bacteria so prepared that the contrast was sharp 

 and the field flat. The cheap way to make successful photomicrographs 

 is to have a complete apparatus : Microscope, stand, lenses, camera, and 

 illuminating appliances dedicated to this one work, mounted to stay, 

 on tables adapted to the purpose, resting on a floor that cannot be jarred, 

 with a fully equipped dark room immediately at hand." An example 

 of Mr. Dennis's high-power work (x 1500) is given. It represents the 



• Journ. New York Micr. Soc, xvi. (1901) pp. 16-7 (1 fig.), 

 t Journ. App. Micr., 1901, pp. 1399-1403 (6 figs.). 



