THE BACTERIOLOGY OF BEE DI8EA1 1 3 



case of gelatin, which solution congeals, as doe- gelatin, on cooling. 

 The milk used is cow's milk with the butter fat removed. Before 

 using, all these media are sterilized by heat to kill all bacteria or fungi 

 which might be present. 



Having prepared these soils in this way, before the inoculation of 

 them the bacteria must be obtained in pure culture. By pure culture 

 is meant the growth of one species only in a medium. Such a cul- 

 ture i- obtained by diluting a small quantity of the material, e. g., 

 decayed larva?, containing the bacteria with a relatively large amount 

 of liquefied agar, and then pouring it into a shallow sterile glass 

 box (Petri dish). In this way we get only a few bacteria scat- 

 tered throughout a thin layer of the medium. Each bacterium then 

 begins to grow, and after a few hours it has produced ;i large num- 

 ber, which, being massed together, we are able to see with the naked 

 eye. This mass of bacteria, having been produced from one individ- 

 ual, constitutes a colony, and such a colony can contain but one spe- 

 cies, therefore we speak of it as pure. Pure cultures are then made 

 by inoculations from such a colony. The next step is to identfy this 

 species which we now have isolated from all other species. To do 

 this we inoculate a few or all of the differential media mentioned 

 above. After inoculating and growing the bacteria in these different 

 media or soils at about the body temperature for a day or longer we 

 observe the effect upon the various media produced by the growth of 

 the bacteria and the appearance of the growth in or upon these media. 

 All these phenomena and appearances we speak of as cultural char- 

 acter-. Having obtained in this way the cultural characters of a spe- 

 cies of bacteria, we are able to classify it by comparing these cultural 

 characters with the cultural characters of known specie-. 



To illustrate this, let us take for example Bacillus coli communis, 

 found normally in the intestine of man and many animals, including 

 the intestine of the adult bee. Bacillus alvei^ found in European 

 foid brood, and Bacillus larva?, found in American foul brood. 

 Bacillus coli con munis by its growth in bouillon causes the latter t<> 

 become heavily clouded: Bacillus alvei makes it feebly clouded; 

 while Bacillus larvce does not grow at all in this soil and the bouillon 

 remains dear. In gelatin Bacillus coli communis grows very well 

 and does not liquefy the medium by its growth; Bacillus alvt i grows 

 wry slowly and only feebly and liquefies the gelatin; while Bacillus 

 larva does not grow at all in this medium. When Bacillus coli com- 

 munis is planted on potato it produce- a brownish growth; Bacillus 

 alvei on this medium produces a lemon-yellow growth, and Bacil- 

 lus larva fail- to -how any growth. When Bacillus coli communis 

 is planted in milk there follow.- a rapid souring of the milk' and a 

 firm coagulation of the casein; Bacillus alvei produce- a .-oft coagu- 



