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 l-12th or l-16th 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 Abbe's con- 

 denser, open diaphragm, and plane mirror. As Koch l pointed 

 out, and what is now universally acted upon, stained specimens 

 mounted in Canada-balsam solution or Dammar varnish, when 

 examined on an Abbii'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 per- 

 fect and reliable one, it is nevertheless important to ascertain 

 as far as possible the appearances, chemical reactions, and 

 general morphology of perfectly fresh specimens. Blood, 

 juices, tissues, and fluids in which the micro-organisms have 

 been growing, are subjected directly, without any previous pre- 

 paration, to microscopic examination. With artificial nourishing 

 media in which micro-organisms have been growing, the ex- 

 amination of fresh specimens is of great importance, for the 

 reason that the organisms can be easily identified and their 

 size and general morphological characters be more correctly 

 ascertained than after drying, hardening, and staining. Besides, 

 the chemical reactions can be satisfactorily studied in fresh 



1 Die Aetiologie d. WundinfectionsTtrnnkheiten. p. 34, Leipzig, 1879. Trans- 

 lat'.-d as Traumatic Infective Diseases (New Syd. Soc.), London, 1880. 



B 2 



