162 



BACTERIOLOGY. 



the microscope when it is in the long axis of the apparatus, so as to 

 make a hglit-tight combination. The opening which is filled in an 

 ordinary camera by the lens can be shut off by means of an internal 

 shutter, which is opened and closed by turning a screw at the side 

 of the camera. The dark-back is provided with plate-carriers, so 

 that either half, quarter, or lantern-size plates can be emiiloyed. It 

 wiU be found convenient to have two or more dark-backs, so that 

 several plates may be exposed without rearranging the hght for 

 each exposure. 



Much more elaborate and expensive micro-photographic cameras 

 have been constructed by Zeiss, and also by Swift. The latter has 



Fiu. 81.— Photogkaph of an Isipkession PEEP.\KATIO^^ 



carried out a suggestion made by Pringle foi- a support at the 

 ocular end (Fig. 80). 



The Bark-room. — In every bacteriological laboratory there should 

 be a developing room provided with shelves, gas, water-tap, and sink, 

 but these arrangements are not absokitely indispensable. All that 

 is essential is a room impervious to light ; and a closet or cupboard, 

 if it can be ventilated, will answer perfectly well, with a jug and 

 basin instead of the tap and sink. The steam-steriliser employed 

 in the preparation of nutrient media for cultivating bacteria, if not 

 I'equired at the time for sucli purposes, may be filled to the brim 

 with water, and will form an excellent cistern and tap, while a pail, 

 or small sanitary bin, may be utilised as a sink. 



Various kinds of lamps are made for the dark-room, burning 



