THE BACTERIOLOGY OF BEE DISEASES. 30) 
vase of gelatin, which solution congeals, as does 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 is obtained by diluting a small quantity of the material, e.g, 
decayed larve, 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 a 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- 
acters. 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 species. 
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 
foul brood, and Bacillus larva, found in American foul brood. 
Bacillus coli communis by its growth in bouillon causes the latter to 
become heavily clouded; Bacillus alvei makes it feebly clouded; 
while Bacillus larvae does not grow at all in this soil and the bouillon 
remains clear. In gelatin Bacillus coli communis grows very well 
and does not liquefy the medium by its growth; Bacillus alvei grows 
very slowly and only feebly and liquefies the gelatin; while Bacillus 
larve does not grow at all in this medium. When Bacillus coli com- 
munis is planted on potato it produces a brownish growth; Bacillus 
alvei on this medium produces a lemon-yellow growth, and Bacil- 
lus larve fails to show any growth. When Bacillus coli communis 
is planted in milk there follows a rapid souring of the milk and a 
firm coagulation of the casein; Bacillus alvei produces a soft coagu- 
