BY R. GREIG SMITH. 



39 



The Influence of Peptone. 



It appears from these results that about 0-5% of peptone in the 

 medium is a good quantity to employ. With a greater percen- 

 tage the growth starts sooner, but as time goes on it becomes 

 slower, and is ultimately surpassed by the lower percentages. 



The reaction of the medium best suited to the bacterium was 

 also investigated, and for this purpose various quantities of 10% 

 tartaric acid and 10% sodium carbonate solutions were added to 

 10 c.c. portions of neutral medium, containing saccharose 5%, 

 peptone 0-5%, potassium phosphate 0-5%, agar 2%. 



The effect of slight differences of acid or of alkali in the culture 

 media is very pronounced. In an absolutely neutral medium the 

 bacteria grow very slowly, while, when the reaction is faintly 

 acid, the growth is quick aijd luxurious. Alkalies prohibit the 



