GROWTH OF BACTERIA IN PROTEIN-FREE PRODUCTS 215 



ptr ctni 



NaCl 0.5 



KH2PO4 0.5 



Sodium citrate 0.2 



MgS04 0.2 



Glucose 5 



Glycerin 6.0 



The media contained 1.5 per cent agar. Plain 1 per cent and 

 2 per cent opsine agar were also used. All of the media were 

 very faintly alkaline to litmus, and inoculations were made from 

 young agar cultures. The growths were recorded after forty- 

 eight hours' incubation. 



The growths on 2 per cent opsine alone were on the whole fully 

 as good as those on 2 per cent opsine plus the above added sub- 

 stances. Every organism out of the large number tried, with the 

 exception of one strain of pneumococcus, grew on opsine alone 

 without beef infusion. The medium containing 1 per cent 

 opsine + beef infusion + the above agents was a little less favor- 

 able for the gonococcus and pneumococcus (save strain 697) than 

 2 per cent opsine + the given mixture, but was decidedly more 

 favorable for B. suisepticus and the streptococcus of equine 

 influenza. In the case of the other organisms there was very 

 little difference. ' 



Experiments were also performed to compare the morphology 

 and viability of cultures on opsine agar with those on fresh beef 

 infusion peptone agar. These two media were prepared with 

 reactions faintly alkaline to litmus, 1 per cent opsine, and 1 per 

 cent peptone and 1.5 per cent agar being used. The cultures 

 were transplanted four times on opsine agar and twice on the 

 beef infusion peptone agar, the medium on which they were 

 accustomed to grow. Pathogenic bacteria were incubated at 

 37° and saprophytic organisms at 24°. Transfers were made 

 every two days. In general, there was little difference in the 

 appearance and luxuriance of the growths on the two media, 

 especially in the last transplants. Differences were distinctly 

 apparent in the following cases : On opsine the growth of Lep- 

 tothrix was wrinkled, while on the control medium it was larger in 

 amount and smooth. B. suisepticus and B. diphtheriae (K.L.) 



