PRACTICAL BACTERIOLOGY. 



quantity of a Chaubert's disease colony with some 

 liquid gelatine in a test-tube. The npper part- of the 

 gelatine remains sterile to a depth of two or three 

 centimetres, whilst the lower portion becomes studded 

 with small globules, filled with a whitish liquid, in 

 which at first a denser nodule may be distinguished. 

 Soon, however, gas-bubbles appear distributed through- 

 out the gelatine ; these alter the appearance of the 

 culture, and break up the medium. In agar-agar a 

 cloudy white thread is developed, which, having no 

 distinct outlines, becomes imperceptibly merged in the 

 medium ; the gas-bubbles appear so soon in this 

 medium that no characteristic appearance can be 

 formed. Occasionally such a violent formation of gas 

 occurs, that part of the agar-agar is lifted right up 

 and is forced, with the plug of cotton-wool, right out 

 of the tube ; this is not of rare occurrence if the 

 culture is kept at blood heat. If a small quantity of a 

 colony of this bacillus taken from an Bsmarch's tube 

 be examined under water with a moderately high 

 power of the microscope, a distinct movement may be 

 observed in some of the cells. The organs of motion 

 may be rendered visible, but the bacilli which are 

 swimming about in the fluid gelatine are not suitable 

 for this purpose, as too much gelatine is transferred 

 with them into the preparation ; this gelatine becomes 

 stained as well as the flagella so that it is hard to 

 distinguish them from one another. It is best to 



