MTKIKNT MKI'IA AND METHODS OF CULTIVATION. 115 



Inoculation of the Tubes. A small portion of a culture or of the 

 material to be inoculated is taken up with a sterilised platinum 

 needle, and traced over the sloping surface of the serum ; or a 

 fragment of tissue, such as diphtheritic membrane or tubercle, may 

 be introduced into the tube and rubbed gently over the serum so as. 

 not to bivak the surface. 



FK;. 44. HUKPPK'S SEKUM INSPISSATOR. 



(D) PREPARATION AND EMPLOYMENT OF STERILISED POTATO. 



Potato-cultivations. -Sterilised potatoes form an excellent 

 medium for the cultivation of many micro-organisms, more especially 

 the chromogenic species. Potato-cultivations al>o give in some cases 

 very oharactrri.-tic appearam-f>, which are of value in distinguishing 

 bacteria which possess morphological resemblances. 



Prepn-'itiim <>f SbrHiMd Potatoes. Potatoes, preferably smooth- 

 skinned, which are free from "eyes" and rotten sput>. should be 

 selected. If they cannot be obtained without eyes ami spots, these 

 must }^' cart-fully picked out with the point of a knife. The potatoes 

 are well x-rubbed with a stiff brush, and allowed to >oak in 1 in _< 

 carbolic for a few minutes. They are then transferred to the potato- 



