82 BACTERIOLOGY. 



(C) PREPARATION AND EMPLOYMENT OF STERILISED 

 POTATOES, POTATO -PASTE, BREAD-PASTE, VEGE- 

 TABLES, FRUIT, AND WHITE OF EGG. 



Potato Cultivations. Sterilised potatoes form 

 an excellent medium for the cultivation of many 

 micro-organisms, more especially the chromogenous 

 species. Potato-cultivations also give in some cases 

 very characteristic appearances, which are of value 

 in distinguishing bacteria which possess morphologi- 

 cal resemblances [Plates IX. and X.] 



Preparation of Sterilised Potatoes. Potatoes, 

 preferably smooth- skinned, which are free from 

 " eyes " and rotten spots, should be selected. If they 

 cannot be obtained without eyes and spots, these 

 must be carefully picked out with the point of a 

 knife with as little destruction of the surface as 

 possible. The potatoes are well scrubbed with a 

 stiff brush and allowed to soak in sublimate solution 

 for half an hour. They are then transferred to the 

 potato-receiver and steamed in the steam-steriliser 

 for twenty minutes to half an hour, varying accord- 

 ing to the size of the potatoes. When cooked, the 

 potato-receiver is withdrawn and left to cool, the 

 potatoes being retained in it until required for use. 



Damp chambers are prepared ready for their 

 reception, the vessels being cleansed and washed 

 with sublimate as described for plate-cultivations. 

 Small glass dishes of the same pattern as the 



