6o SOLID CULTIVATION MEDIA. 



be used for each potato, and, immediately before use the blade must 

 be heated red hot, and then placed to cool, with its edge upwards, 



Fig. i8. — Micrococcus of acute osieo-myeli/is growing on sterilised 

 potato. The yellow pigment consists of irregular granules, which lie 

 around and not within the individual cells of the growth. 



projecting over the side of a table, so as to offer as small a surface 

 as possible to the gravitating atmospheric germs. 



The potatoes being now cool enough for manipulation, the operator 

 cleanses his hands thoroughly with corrosive solution (i-iooo), and, 

 getting an assistant to raise the Hd slightly for a moment in a verti- 

 cal direction, removes one potato from the holder. The potato is 

 grasped in its shortest diameter (see Fig. 20), and, thus held, it is cut 

 through in its longest diameter by a single steady sweep of one of the 

 sterilised knives. The assistant now raises the lid of one of the 

 sterile bells, slowly and perpendicularly, and when the knife has all 

 but completely divided the potato, the latter is laid on its side on the 

 floor of the chamber, and its upper cut half is opened up, hinge-like, 

 by the blade of the knife, and laid alongside the lower half of the 

 potato with its large smooth - cut surface upwards. The cut sur- 



