SIMPLE APPARATUS FOR PHOTOMICROGRAPHY 227 



omnibuses is established in the vicinity, this method no longer 

 serves its purpose, and other means must be sought. 



The second set of troubles has quite a different cause, 

 arising from the use of aniline dyes to stain in a selective 

 manner different parts of animal tissues. As happens in 

 ordinary photography, these colours appear to the photographic 

 plate in a different manner from that in which they do to the 

 eye, and to get the best contrast in the negative requires some 

 preliminary experimenting with coloured screens, which may 

 be interesting from an optical standpoint, but which causes 

 much loss of time when what is wanted is merely a photograph 

 of the object under examination. 



These difficulties can be avoided if the apparatus is slightly 

 modified in the manner indicated below, and the modifications 

 have been tested by actual work with the photomicrographic 

 apparatus at St. Mary's Hospital for some time. 



The camera, of any convenient type {e.g. Zeiss or Leitz), was 

 fixed to a solid base-board of 2-in. mahogany, 8 ft. long and 

 11 in. wide. Underneath this was a second board, 6 ft. by 12 in. 

 by 2 in. To the ends of this were fixed four stout staples, and 

 by means of these the whole apparatus was hung from the ceiling 

 by 20 to 22-gauge copper wire. Other description is unnecessary, 

 beyond saying that it is well to have the base of sufficient 

 stiffness, otherwise the apparatus sags in the middle, and so 

 throws the optical parts out of centre. Further, the supporting 

 wires should not be of too coarse gauge, due regard being had 

 to the weight they have to bear; and it is prudent to have a 

 duplicate set quite loose, so as to support the apparatus if the 

 first set should happen to break by any mischance. 



The result of this suspension is twofold. In the first place 

 most of the vibration is taken up by the wires, and even when 

 the building is shaken violently by the trains below, a glass 

 of water on the camera hardly ripples. But a more important 

 effect is that any residual vibration affects all the apparatus 

 on the base-board synchronously, and no one part is displaced 

 relatively to any other, the net result being that even in test 

 photographs of diatoms taken at 1,000 diameters, and in 

 Mr. Fantham's l photographs of Piroplasma Bigeminum at 

 1,200 diameters there was no trace of shake. 



1 Fantham, H. B., Quart. Journ. Micros. Sci. vol. li. pt. ii. 1907, p. 297. See 

 also Ridewood, W. G., and Fantham, H. B., loc. cit. vol. li. pt. i. 1907, p. 81. 



