134 



Trypsin. 



A peptonizing- ferment must be present, since gelatin and Loeffler's 

 solidified blood serum are liquefied, and casein is slowh' dissolved 

 with the formation of tyrosin. This, also, is secreted in minute 

 quantities or else is partially inhibited by other substances, because 

 gelatin is liquefied very slowly even under favorable conditions — i. e.. 

 optimum temperature, proper alkalinity, and suitable food. 



Ps. caiiipestria and Ps. phaseoli behave in the same way — i. e.. they 

 liquefy gelatin and Loeffler's solidified blood serum and dissolve 

 (peptonize) casein. These processes take place more rapidly than in 

 case of Ps. hyacinth), but in none of them is the peptonization speedy. 

 Ps. steicarti does not liquefy gelatin or Lceffler's solidified blood 

 serum. 



Lab Ferment. 



The existence of a lab or rennet ferment is at once suggested by the 

 fact that in milk cultures the casein is thrown out of solution in the 

 absence of any visible production of acids (see Milk and litmus milk 

 and Litmus under reduction experiments). The casein is also pre- 

 cipitated if the whey from old alkaline milk cultures is first sterilized 

 by heating it for ten minutes at 56^ C. and then added to tubes of 

 sterilized milk along with th^-mol. Media inoculated from the thus 

 coagulated milk remained sterile. 



The same whey, after heating for ten minutes at 90^ C, had no 

 efiect upon milk. 



Ps. eamj^estris and Ps. jyhaseoli behave in the same way. Both 

 throw down casein by means of a lab ferment. Ps. steicat'tL on the 

 contrary, produces no lab ferment and never coagulates milk. 



Oxidizing Enzymes. 



Xo oxidase or peroxidase was detected — i. e.. the cultures of Ps. hya- 

 eirdhi did not react blue with sensitive guaiac resin in alcohol nor was 

 there any bluing on the subsequent addition of hydrogen peroxide. 

 Ps. campestris behaved in the same way. The brown stain is believed 

 to be due to other causes. 



A copious evolution of gas bubbles took place when hydrogen perox- 

 ide was added to old potato cultures of Ps. Jiyacinthi., P^. ca.mpc.'<tr!s. 

 Ps. phase<Ai and Ps. steinartl. 



Such copious evolution of oxygen is. however, not peculiar to these 

 particular parasites. It has been more recently observed by the writer 

 in case of old potato cultures of Bacillus coli^ B. amylovarus., B. pyo- 

 cyaneus pjevicarditiclis. a fluorescent germ obtained from fermenting 

 tobacco and able to grow in the presence of thymol. Earle's bacillus of 

 tomato fruit rot. an orange colored cUunpy organism from cotton 



