12 ATLAS OF NERVE CELLS 



THE PHOTOGRAPHIC TECHNIQUE 



BY EDWARD LEAMING, M.D., F.R.P.S. 



INSTRUCTOR IN PHOTOGRAPHY, COLLEGE OF PHYSICIANS AND SURGEONS, COLUMBIA COLLEGE. 



IN photomicrography it is essential that the optical parts of the apparatus used, termed 

 the system, should have their centres in the same straight line, and that this system, together 

 with the camera, should be so mounted as to be as rigid and free from vibrations or accidental 

 displacement as possible. These conditions were fulfilled by the apparatus used, which was 

 the large photomicrographic outfit of Carl Zeiss of Jena, in the laboratories of the College 

 of Physicians and Surgeons. 



This consists of two heavy iron stands, upon one of which rests the camera, supported 

 by wheels, so that it can be rolled backward and forward without being displaced laterally ; 

 thus the operator is enabled to observe the object directly through the microscope without 

 altering the centring of any of the parts of the system. The second stand supports a broad 

 table, upon which is the microscope, inclined to the horizontal position, and an optical bench 

 of two parallel metal rails, upon which are fastened by set screws the accessory parts of the 

 system. These vary with the work, but are usually coloured light niters for altering the white 

 light to a monochromatic light, or screens for otherwise modifying it, diaphragms for centring 

 and for limiting the size of the light pencil, condensers, and reflecting mirror. The electric 

 arc used was so made as to fit the optical bench and be mechanically centred both laterally 

 and vertically. The weight of the two stands insured rigidity, and the mechanical adjustments 

 of the different parts were easily made, so that a beam of light from the electric arc or 

 from the heliostat would pass through the optical centres of the system of lenses and be 

 projected upon the centre of the ground glass screen of the camera. Where possible, sunlight 

 reflected from the speculum of an heliostat was the illuminant, and was used in preference 

 to other sources of illumination ; but, as in these latitudes during the winter season there 

 are many dark and cloudy days, it was found necessary to resort frequently to the electric 

 arc, which, as recently improved, gave results that left little to be desired. 



It would seem at first, as the Golgi stain is a metallic impregnation and opaque, that 

 the use of isochromatic plates and a colour screen would have been unnecessary, but those 



