156 



BACTERIOLOGY. 



all the purposes for which the apparatus may be required, iucluding 

 the employment of the highest powers, and also that one may be 

 enabled to work for long intervals of time with due comfort, an 

 accurate and complete apparatus will be found to be most desirable. 

 Though most preparations will admit of being photographed 

 when the stage of the microscope is vertical, yet if we require to 

 photograph micro-organisms in liquids, or colonies upon partially 

 liquefied gelatine, the apparatus must admit of being placed so that 

 the stage of the microscope becomes horizontal. In addition, the 

 apparatus is rendered somewhat complex if we employ powerful 



Fig. 77. — Hokizontal Micko-photogeaphic Apparatus. 



artificial Hght. Sunlight, no doubt, is the best and cheapest, but 

 it is not always available, especially in a city like London; and, 

 moreover, evenings and dull days will probably be the very time 

 which can be best spared for this work. We must, therefore, fall 

 back upon the paraffine lamp, or the magnesium, oxyhydrogen, or 

 electric light. 



To fulfil all these conditions Swift has constructed an apparatus 

 under the author's du-ections (Fig. 78). It is merely a modification 

 of the ordinary horizontal model, which admits of being readily placed 



