A SIMPLE APPARATUS FOR PHOTO- 

 MICROGRAPHY 



By N. H. ALCOCK, M.D. 



The use of the camera instead of the pen in preparing diagrams 

 of microscopic preparations is gradually becoming more common, 

 in spite of the numerous disadvantages that at first attended 

 the process. Some of these arise from the nature of the method, 

 and cannot be circumvented by the exercise of ingenuity. For 

 example, the photographic plate records only one plane of the 

 object, whereas a practised observer by the aid of the focussing 

 screw can bring several planes into view at once, and so it 

 happens that for some purposes, such as counting the chromo- 

 somes in an individual cell, photography is much inferior to 

 simple vision. For other purposes, however, this peculiarity 

 is rather of advantage than otherwise, and the superior accuracy 

 and freedom from bias of the photographic method are bringing 

 it more and more into use. Further, a drawing contains only 

 what the observer sees, while the camera shows everything that 

 is there, whether the observer has noticed it or not, and so 

 forms a much more complete record of the preparation than 

 a simple drawing. 



When one attempts to take a photograph through the 

 microscope in the ordinary way, a second set of difficulties 

 occurs, which, while not in any way essential to the process, 

 yet commonly gives rise to much loss of time and trouble. 

 Two of these may be briefly noticed. The first arises from 

 slight tremors of the building, which are communicated to the 

 camera, and when high magnification is employed become very 

 troublesome. This can to a great extent be avoided if the 

 whole apparatus be placed on a concrete pillar, solidly built 

 up from the ground, and passing through the floor of the 

 building in which it is placed without actual contact. But 

 if the Metropolitan Railway passes immediately underneath, 

 as happens in one laboratory in London, or if a line of motor 



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