116 



BACTERIOLOGY. 



receiver, and steamed in the steam steriliser for twenty minutes to 

 half an hour, the time varying according 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 When cooked, the potato-receiver is withdrawn and left to cool, the 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 the potatoes, the vessels 

 being cleansed and washed with carbolic as described for plate- 

 cultivations. Small glass dishes of the same pattern as the large 

 ones may be employed for single halves of potatoes. Potato-knives 

 and scalpels, which have been sterilised in an iron box by heating 

 them in the hot-air steriliser at 151° C. for one hour, should 

 be ready to hand. Knives sterilised by heating them, in the flame 

 of a Bunsen burner should afterwards be placed upon a sterilised 

 glass plate and covered with a bell-glass. It mvist not be forgotten. 



I A^\ 



Fig. 45. — Box I'OK Sterilising Instkhments. 



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, enclosed in an iron 

 box, or simply enveloped in cotton-wool. 



Inoculation of Fotatoea. — The coat-sleeves should be turned back, 

 and the hands, after thorough washing with good lathering soap, 

 be dipped in 1 in 40 carbolic. An assistant opens the potato- 

 receiver, and a potato is selected and held between the thumb and 

 index ringer of the left hand. 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 the 

 knife is withdrawn, allowed to fall apart. The cover is quickly 

 replaced, and another potato treated in the same way, is placed 

 in the same damp chamber. The four halves are then quite ready 

 for inoculation. As an extra precaution, the left hand is again 

 dipped in carbolic, and one half of a potato is taken up between the 

 tips of the thumb and index finger, care being taken to avoid 

 touching the cut surface. Holding it with its cut surface vertical, 



