158 



PLANT PARASITES. 



acquaintance with methods and apparatus in a well-appointed laboratory, than to make 

 the attempt to work out the methods from books. 



The methods of inoculation of animals with pure cultures, and the precautions to 



FIG. 82. PETRI'S AGAR PLATE CULTURE OF BACTERIA FROM THE MOUTH. 



Made by streaking the surface of sterilized nutrient agar previously poured into the shallow dish and 

 cooled with scrapings from the mouth, and allowing to stand in a warm place for forty-eight hours. The 

 lighter spots are the " colonies " or masses of germs of various forms which have grown from the invisible 

 germs of the mouth. 



be observed, as well as a description of the various forms of apparatus made use of in 

 practical bacteriology, must be sought in more extended treatises on this subject. 



Collection of Material for Bacterial Cultures. 



Material obtained from the human body which is to be subjected to bacterial ex- 

 amination should be collected with every precaution against accidental contamination. 



FIG. 83. STERILIZKD COTTON SWAI 



A STERILIZED TUBE FOR COLLECTING FLUIDS CONTAINING BAC- 

 TERIA. 



A convenient mode of collection and transportation of small quantities of fluid or 

 semi-fluid material, such as exudates, discharges, etc., for purposes of bacterial examiua- 



