PHOTOGRAPHY OF BACTERIA. 169 



be obtained, whereas an original drawing, even in the best hands, 

 if cut on wood or lithographed, is almost certain to fall short of 

 being an exact copy. 



With regard to individual bacteria, the result is more satisfactory 

 in many cases than a drawing ; for there is the advantage of being 

 absolutely certain that any particular structure, form, or shape 

 which may be represented is actually what exists, and not what 

 may have been evolved by unconscious bias in the mind of the 

 observer. Many illustrations might be given of this. Thus Lewis, 

 who was a most conscientious observer, published an account of 

 organisms in the blood of rats in India, and illustrated it with a 

 wood engraving and with micro-photographs. The identity of the 

 organisms which were found in the common brown rat of this 

 country was established much more readily from these photographs 

 than from the wood engraving or the description in the letterpress. 



A micro-organism, even under the highest powers, appears as 

 so minute an object that to represent it in a drawing requires a 

 very delicate touch, and it is only too easy to make a picture which 

 gives an erroneous impression to those who have not seen the 

 original. If, on the other hand, to represent the object more 

 clearly we draw an enlarged picture, we can only do so by repre- 

 senting what we think the object would be like if it could be 

 amplified to the size represented. In such cases a photographic 

 enlargement is certainly more valuable. 



Photography enables us also to record rapid changes, and it 

 is possible that as the art advances we may find that the film is 

 more sensitive than the human retina, and brings out details in 

 bacteria which would be otherwise unseen. 



Photographs can be readily transmitted by post, and when we 

 can neither make a great number of preparations to illustrate 

 some object, nor perhaps be able to go to the expense of having a 

 drawing reproduced, this method will be of value in enabling others 

 to benefit by our observations. 



The author is convinced that if the employment of photography 

 is encouraged in bacteriological and other research laboratories for 

 depicting microscopical preparations and cultivations of bacteria, the 

 results of increasing experience and practice will lead to its being 

 made more general use of as a faithful and graphic method, valuable 

 alike for class demonstrations and for illustrating publications. 



