RELATION OF PATHOGENIC TO SEPTIC BACTERIA. 19 



formation are present, the amount of air present in the glass 

 cell sufficiently large to enable the spore formation. 



As in my former work so also now, I use olive oil to fix the 

 cover glass over the glass ring forming the sides of the cells. 

 The cover glass before being used is well heated over the flame. 

 A small quantity of the nourishing fluid (pure pork broth or 

 liquefied gelatine pork) is withdrawn from the stock flask by a 

 freshly drawn-out small capillary pipette; this is eff"ected in 

 this manner : the cotton-wool plug of the stock flask is drawn 

 up for about half its length, and the one end of the pipette 

 being drawn out into a long capillary tube is gradually pierced 

 through the remaining half length of the plug and pushed 

 down till it reaches the fluid ; the pipette is filled and with- 

 drawn, and the plug is again pushed down into its previous 

 position. By this means absolutely no access is allowed to 

 particles from the air into the stock flask, and at the same time 

 the capillary tube, while being pushed through the cotton^wool 

 plug, is cleaned from accidentally adhering particles. It must 

 be borne in mind that for the above purpose the cotton wool 

 must have been well sterilised by heat, because if not so, 

 the nourishing material in the stock flask is sure to become 

 contaminated by impurities adhering to the cotton-wool fibres, 

 some of these being pushed down as well as carried down into 

 the fluid by the capillary tube. From this pipette a drop is 

 quickly deposited in the centre of the cover glass, and this is 

 inverted and fixed on the ring of the glass cell, a drop of dis- 

 tilled water having been previously placed at the bottom of the 

 cell at a peripheral place. The cell is now " charged " and 

 ready to receive the organism that is to be cultivated in the 

 drop of nourishing material attached to the centre of the lower 

 surface of the cover glass. The process of charging the test- 

 tubes and flasks, as well as the glass cells, being carried out 

 in the air, is of course subjected to the complication of :i con- 

 tamination with air organisms. In the case of the test tubes 

 and flasks this is remedied by subsequent boiling of the 

 charged and plugged vessels ; but in the case of the glass cells 

 a sterilisation after charging is for obvious reasons impossible, 



