66 MICRO-ORGANISMS AND DISEASE [chap. 



of bacilli, and of fungi, and other life processes can be 

 watched and noted. I have made very extensive observations 

 on the growth and division of bacilli and of mycelial fungi, 

 extending for hours, and noting the progress from day to 

 day, by distributing a limited number of the microbes (by 

 the aid of the point of a thin platinum needle) in a droplet 

 of melted nutrient gelatine or Agar deposited in the centre 

 of the cover-glass,! and then flattening the droplet by the 

 platinum needle out into a film, of course limited to the 

 centre of the cover-glass, and finally fixing this latter by 

 means of sweet oil to the glass side film downwards. The 

 gelatine, as also the Agar, sets at the ordinary "temperature 

 of the laboratory, and by a power up to 700 the bacteria 

 or other microbes can be easily focussed and kept under 

 observation, they being fixed in the set gelatine or Agar. 



The glass cell (see Fig. 13) which I use is based on the 

 same principle ; it has the advantage of allowing the ob- 

 servation to be extended over longer periods as it is easier 

 to keep the chamber of the cell moist by depositing a droplet 

 of water on its floor. 



These methods of watching and studying bacteria and 

 fungi in the living state with high powers in a gelatine film or 

 Agar film cannot be too strongly recommended ; it can be 

 carried out and extended over hours and days. A direct 

 insight is obtained into the phenomena of growth, germina- 

 tion, and division, as also of spore formation which as a 

 rule is only indirectly deduced. It is one of the most in- 

 teresting experiments to make such a preparation from the 

 blood of an animal dead of anthrax (care being taken to 

 introduce only a limited number of bacilli), and to watch 



^ If a culture is used it is best first to make a distribution in sterile 

 salt, or water, or broth, by shaking in it a small particle of the growth 

 transferred by a platinum needle, and to inoculate the gelatine or Agar 

 drop from this dilution. 



