CHAPTER I. 



MICROSCOPIC EXAMINATION. 



FOR the examination of micro-organisms good high powers 

 are essential, at the least a power magnifying 300 to 400 

 linear diameters. Zeiss' D or E and Zeiss' or Powell and 

 Lealand's oil immersion i-i2th or i-i6th inch will be found 

 sufficient for all purposes. In the case of tissues stained with 

 aniline dyes a good substage-condenser such as Abbe's or 

 Powell and Lealand's, is invaluable. I use Zeiss' stand 

 with Abba's condenser, open diaphragm, and plane mirror. 

 As Koch 1 pointed out, and what is now universally acted 

 upon, stained specimens mounted in Canada-balsam 

 solution or Dammar varnish, when examined on an Abbe's 

 condenser, show the micro-organisms with extreme clearness 

 and sharpness. 



The examination of the morphological characters of an 

 organism is carried out on fresh unstained, as well as on fresh 

 stained, microscopic specimens. Although the latter method 

 is, for reasons hereafter to be mentioned, by far the most 

 perfect and reliable one, it is nevertheless important to 



1 Die Aetiologie d. Wundinfectionskrankheiten, p. 34, Leipzig, 1879. 

 Translated as Traumatic Infective Diseases (New Syd. Soc.), London, 

 1880. 



