CHAPTER IV 



METHODS OF INVESTIGATING MICROBIAL DISEASES THE 

 INOCULATION AND DISSECTION OF ANIMALS HANG- 

 ING-DROP CULTIVATION INTERLAMELLAR FILMS 

 THE MICROSCOPE. 



THE systematic study of a condition dependent on the 

 activity of micro-organisms is in many instances no light 

 matter. When only one or two forms are present and 

 these are readily cultivated it may be comparatively 

 easy, but when there are many the investigation may 

 become exceedingly complicated. The first step to be 

 taken is to ascertain by careful microscopical examination 

 whether micro-organisms be present, and if so, their 

 general characters, and their distribution, both in fresh 

 unstained and in stained preparations, and if possible at 

 different stages of the disease. In disease conditions, 

 for example, the blood and secretions may be examined 

 both before and after death, but in the latter it must be 

 remembered that soon after the fatal event adventitious 

 organisms rapidly make their appearance, gaining access 

 from the air and from the intestinal tract. If organisms 

 be detected an attempt should be made to determine 

 whether there is any predominant form and if this is 

 constantly present at different stages. If organisms are 

 found, it simplifies matters, but if not, it cannot therefore 

 be said that they are absent, for they may be relatively 

 few in number or be in a degenerate condition, and 

 consequently be missed in a microscopical examination ; 

 or they may be confined to a particular locality or tissue, 



