PREPARATION OF POTATOES. 



85 



Fig. 15. 



by twisting the knife gently the two halves of the 

 potato may be caused to fall apart in the dish and 

 usually to fall upon their convex surfaces, leaving the 

 flat sections uppermost. The cover is placed upon the 

 dish and the potatoes are ready for inoculation. 



2. Preparation of potatoes for test-tube cultures. Method 

 of Bolton.^ If the potatoes are to be employed for test- 

 tube cultures, one simply scrubs ofl" the coarser particles 

 of dirt with water and a brush, and with a cork -borer 

 punches out cylindrical bits of potato which will fit 

 loosely into the test-tubes to be used. 

 On each bit of potato is then to be cut a 

 slanting surface running diagonally from 

 about the junction of the first and second 

 third of the cylinder to the diagonally 

 opposite end. These cylinders of potato 

 are now to be left in running water over 

 night, otherwise they are very much dis- 

 colored by the sterilization to which they 

 are to be subjected. At the end of this 

 time they are placed in previously pre- 

 pared test-tubes, one piece in each tube, 

 with the slanting surface up, the cotton 

 plugs of the tubes replaced, and they 

 are then to be sterilized in the steam 

 for forty-five minutes. On the second 

 and third days they are to be sterilized 

 for fifteen to tweaty minutes each day. 



The entire sterilization may be accom- 

 plished in the autoclave with the steam under a pres- 

 sure of one atmosphere, by a single exposure of twenty 



Potato In test-tute. 



1 Medical News, 1887, vol. 1. p. 138. 

 5 



