PREPARATION OF NUTRIENT MEDIA. Sj 



large ones (Fig. 13) may be employed for single 

 halves of potatoes. Potato knives and several 

 scalpels which have been sterilised in an Israel's 

 case by heating them in the hot-air steriliser to 150 

 for one hour, must be ready to hand. The potato 

 knives may also be sterilised by heating them in 

 the flame of a Bunsen burner and placing them 

 on their backs with their blades projecting over 

 the edge of the table. Scalpels may be sterilised 

 in the same way and laid upon a sterilised glass 

 plate and covered with a bell-glass. It must not 

 be forgotten, however, that heating the blades in 

 the flame destroys the temper of the steel, and 

 therefore knives and other instruments should 

 preferably be sterilised in the hot-air steriliser^ en- 

 closed in an Israel's case, or simply enveloped 

 in cotton wool. 



Inoculation of Potatoes. The coat sleeves 

 should be turned back, and the hands, after a 

 thorough washing with good lathering soap, be 

 dipped in sublimate solution. An assistant opens 

 the potato receiver, and a potato is selected, 

 and held between the thumb and index finger 

 of the left hand (Fig. 30). With the knife held in 

 the right hand, the potato is almost completely 

 divided in the direction which will give the largest 

 surface. The assistant raises the cover of the 

 damp chamber, and the potato is introduced, 

 and while withdrawing the knife, allowed to fall 

 apart. The cover is quickly replaced, and another 



