56 



A MANUAL OF BACTERIOLOGY 



tion of mercuric chloride ; a hole is chipped at one 

 end of the egg, and the membrane cut through with 

 a pair of sterilised scissors. The exposed egg 

 albumin is inoculated by means of a platinum or 

 glass needle. The opening is covered with a piece 

 of sterilised paper or cotton wool, which is then 

 painted over and sealed with surgical collodion. 

 The egg is then placed in an incubator. 



Cooked potatoes 

 are also used for cul- 

 tivation purposes. 

 The potatoes 

 (smooth -skinned) 

 are scrubbed and 

 the so-called eyes 

 removed by a sharp 

 knife. They are now 

 soaked for twenty 

 minutes in a solu- 

 tion of mercuric 

 chloride (1 in 1000); 

 washed in water, 

 and then cooked in 

 a steam steriliser for 

 thirty minutes. After cooling, the potatoes are cut 

 by a knife previously sterilised in the naked flame, 

 or in Israel's box placed in a hot-air steriliser. The 

 potatoes are cut 1 through the middle, and the two 

 halves of each potato are then placed in previously 

 sterilised damp chambers (Fig. 22). 



1 The hands during this operation should have been pre- 

 viously dipped into a solution of mercuric chloride. 



FIG. 22. DAMP CHAMBER. 

 (For plate-cultivation, etc.) 



