278 Transactions of the Society. 



same long threads are also occasionally seen as in fig. 23 ; in this 

 case the organism took the Gram's stain fairly well. 



When grown on glucose formate agar, a medium especially 

 congenial to this organism, the size of the rods is extreme (fig. 24), 

 and the staining is very dark ; later in two or three days the 

 staining may become mottled or Gram granular (fig. 25), and this 

 characteristic is seen in impure cultures made from wounds before 

 plating out (fig. 22). All these three types of organisms are met 

 with in septic wounds and tend to persist in the scattered frag- 

 ments of bone and coarse granulation tissue (fig. 5, PL XIX) 

 developing in the process of healing. 



The series of slides I have shown more than prove my contention 

 of the great advantage derived by the use of photomicrography in 

 the prosecution of bacteriological research, more especially when 

 so varied a series of problems presents itself for elucidation. 

 From a technicological point of view — and it is mainly for this 

 purpose that I have brought them to notice — this series of slides 

 illustrating extremely varied subjects shows v/hat may be accom- 

 plished by careful consideration of the optical problems involved — 

 the use of the appropriate colour screens and standard methods of 

 development and exposure which have been adopted throughout. 

 A standard magnification of 1,000 diameters for the bacteria and 

 500 for the tissues and sections is used to enable exact comparison 

 of individual slides. The methods of staining have also been 

 standardized as far as possible, and much valuable knowledge has 

 been obtained in the mere technique of staining by the close 

 attention to the fact that the preparations were required for 

 photography. All the technical details of the photography 

 enumerated above have been carried out by Mr. Cyril Hill, to 

 whom I tender my liearty thanks for his painstaking co-operation. 



