126 31anual of Veterinary Microbiology. 



Potatoes. 



Some germs admit of cultivation upon the potato. 

 For the preparation of fliis medium sound tubers 

 with smooth skin are selected, thoroughly washed in 

 water with a brush, and allowed to soak some time 

 in 1 to 1,000 sublimate solution. They are then 

 cooked by steam at 100°, or in the Chamberland auto- 

 clave, cut in two with a previously flamed table- 

 knife, and deposited in a moist chamber. 



A moist chamber is usually represented by two 

 crystallizers of different sizes, and well disinfected ; a 

 piece of filter paper saturated with sublimate solution 

 is placed in the smaller, which is then covered by the 

 larger. We thus obtain a moist space protected from 

 the atmospheric germs. 



Sometimes potatoes, cut in sections, are cooked in 



tubes ready for culture ; these have a constriction 



near the base to retain the potato about the middle 



of the tube. 



Methods of culture. 



In order to cultivate germs we must first 'possess 

 pure sowings. Occasionally the germ may be ob- 

 tained pure from the organism in which it has de- 

 veloped, as, for example, in bacteridian charbon, 

 chicken cholera, rouget of the pig, etc. 



In most cases the micro-organisms do not occur in 

 a state of complete purity in the parts of the organ- 

 ism in which they pullulate ; it then becomes neces- 

 sary, first of all, to separate them from other germs. 

 We have, therefore, to describe, successively, the 

 methods of isolation of germs, the inoculation of the 



