PHOTOGRAPHY OF BACTERIA. 151 



his disposal in the Museum at Washington, enabled him to obtain 

 photographs of diatoms which probably have never been surpassed. 



To Koch belongs the credit of being the first to extend the 

 application of micro-photography to the delineation of bacteria. 

 A series of instructive photographs was first published by him 

 in 1877. These were photographs of cover-glass preparations, 

 and all admirably illustrated the subjects from which they were 

 taken ; while two, showing the flagella of bacilli and spirilla, 

 were triumphs in this new departure. 



Lewis, in India, was one of the first to illustrate his writings on 

 the subject of micro-organisms by means of photographs. 



About the same tim.e Sternberg, in America, took some excellent 

 photographs of bacteria. Heliotyps reproductions of these were 

 published in 1884. 



Hauser and "Van Ermengem and many other bacteriologists 

 successfully resorted to photography for illustrating their researches, 

 and Frankel and Pfeiffer's, and Itzerott and Niemann's atlases of 

 photographs of bacteria, in microscopical specimens and cultivations, 

 are especially worthy of mention. 



Opinions have differed widely as to the merits of photographic 

 illustrations. Many, taking the standpoint solely of a comparison 

 with drawings, have decried their use. By judging from such a 

 comparison alone the real value of photographs may be lost sight 

 of. On the other hand, many who have looked at the question 

 from all sides, have been led to value even a defective photograph 

 more than an ordinary drawing. 



In his first publication on this subject, Koch strongly advocated 

 photography on the ground that illustrations would then be as true 

 to nature as possible. The photographs which accompanied his 

 paper were all taken from preparations of bacteria which had 

 been made from blood, cultivations, or infusions, by drying a 

 thiri layer on a cover-glass and staining, or from specimens prepared 

 in the same way but left unstained. But when, having committed 

 himself to this opinion, Koch attempted, later, to photograph the 

 bacteria in animal tissues, he was led to modify his previous 

 conclusion. For though no trouble was spared, yet disappointing 

 results were met with. This was owing, he explains, to the fact 

 that the smallest and most interesting bacteria can only be made 

 visible in animal tissues by staining them, and thus obtaining the 

 advantage of colour. 



This introdviced the same diificulties which are met with in 

 photographing coloured objects, such as tapestry and oil paintings. 



