138 SUMMARY OF CURRENT RESEARCHES. 



Staph, pyog. albus. The results of the experiments are regarded as 

 satisfactory in respect to the antibacterial and disinfecting properties. 



Measuring Bacteria.* — Dr. E. H. Wilson and Mr. R. B. F. Ran- 

 dolph describe a simple and accurate method for measuring bacteria by 

 means of photography. The photographic apparatus is adjusted for an 

 amplification of 1000 diameters, by measuring the magnified image of a 

 stage micrometer on the ground-glass screen (figs. 38, 39). " A drawing 

 is made of a convenient size by ruling with ink two sets of equidistant 

 lines at right angles to each other, each tenth line being somewhat 

 heavier than the others ; this drawing should be at least four times the 

 size of the negative to be prepared from it, in order to secure the 

 requisite fineness of the lines. The drawing is then reduced by photo- 

 graphy to such a size that the rulings are exactly one millimetre apart. 

 The negative so obtained is the scale used. The image of this scale is 

 superposed on the image of the photomicrographic negative by a pro- 

 cess of double printing, the photomicrographic negative being printed 

 first, and the scale afterwards on the same paper, or vice versa. The 

 amplification being 1000 diameters and the scale being in millimetres, 

 the reading is directly in micromillimetres." 



* Jouru. Applied Microscopy, 1899, pp. 598-9 (2 figs.). 



