36 Transactions of the Society. 



figures witli the camera lucida, I have employed an amphfication 

 of 2000 or 2400 diameters obtained with the 1/16 or 1/20 

 immersion objective, and a 1 in. or 3/4 in. eye-piece. Though it is 

 easy to obtain very much higher magnification by various methods, 

 little is gained thereby in the examination of structure, and even 

 with the powers here employed everything depends upon the 

 methods of illumination. 



From this demonstration it will be seen how difierent are the 

 appearances of one and the same microbe, not only under the action 

 of different reagents and methods of preparation, but even under 

 difierent magnifying powers ; this shows the absolute necessity in 

 investigating such organisms, of examining them under difierent con- 

 ditions, and in the first instance, always in as natural and unaltered 

 a state as possible, to learn their true characters, which are fre- 

 quently materially altered by the mere process of drying on the 

 cover-glass. It should also induce caution in pronouncing two 

 microbes to be specifically distinct, from apparently slightly 

 difierent characters ; a tendency to do this with the result of 

 obscuring the subject and retarding scientific progress has recently 

 been conspicuous in at least one important micro-pathological 

 investigation. 



Lastly, with respect to the systematic position of the microbe 

 here in question, it scarcely answers completely to the characters 

 of any one of Cohn's genera; it certainly is not a Micrococcus, nor 

 is it a Bacterium ; it is rather a Bacillus as shown by the length 

 of the cells, but it has not yet been observed to form spores as the 

 typical species of this genus do ; I should therefore prefer to term 

 it simply, at present, the microbe of chicken cholera. 



