BACTERIOLOGY. 169 



Urine and water are examined in the same way (in 

 general the vessels are cleaned). 



Filtration of bacteria is an important process in the 

 study of the organisms. It is done by means of a por- 

 celain tube which is the only perfect filter known. 

 Watch the demonstrator use the filter. 



Examine water for Bacteria. Take the water and 

 place it in the plating dish and after a time count the 

 colonies. 



Method: Take a definite quantity of water and 

 put it in a dish of agar-agar; put the same in an 

 incubator for twenty- four hours; take out and count 

 the colonies with the aid of a lens. Each colony re- 

 presents a single germ. 



Practical Use of the Analysis. First, we find the 

 B. Coli and B. Typhosus in water. The earth is an- 

 other place where we find a great number of bacteria, 

 i. e., the B. tetani. 



DETERMINING THE THERMAL DEATH POINT OF BAC- 

 TERIA. 



This is a simple procedure. Take some bouillon 

 and inoculate it with some living bacteria; place it in 

 a water bath and introduce a thermometer; turn on 

 the gas and note the temperature; when the tempera- 

 ture reaches the body temperature take out one of 



