EXPERIMEJNT STATION REPORTS. 



177 



The samples were then shaken and tested quahtatively for tyrosin by 

 Fohn and Denis' Reagent. In recording the results I have used one plus 

 sign to indicate the weakest shade of blue, which corresponds to a negative 

 test, as is shown by the fact that uninoculated milk gave a light shade of blue' 

 with the reagent. The following are the results of this test : 



D. A. + + 

 D. B. + + 

 D. C. + (negative) 

 Sp. A. ++ + 

 Pv. A. + + + 

 Pv. B. + + + + 

 Pv. C. + + + + 

 Pv. D. + (negative) 



Uninoculated milk + (negative) 

 Tyrosin in water + H — | — |- 

 Tyrosin in milk + -| — h 

 Typtophane in water + + + 

 Typtophane in milk -\ — h 

 Merck A. + + + 

 Merck B. + (negative) 

 Merck C. + + 

 B. A. + (negative) 



B. B. + + 

 B. C. + + 

 B. D. + (negative) 



It will be observed that typtophane gives the reaction as well as tyrosin. 

 According to Abderhalden oxy-typtophane and 1-oxyproUn also give a blue 

 color with this reagent. I know of no test for the two latter substances but 

 I performed a test for typtophane with bromine water. The following 

 results were secured: 



From the foregoing it will be seen that a more specific reagent was neces- 

 sary to determine whether the substance giving a blue color with Folin and 

 Denis' Reagent was in reahty tyrosin or something else. In some of 

 the cases it is clearly due to typtophane, so a glycerin extract of tyro- 

 sinase from wheat bran was prepared. This, along with some of the bran 

 itself, was added to a portion of each sample and to suitable positive and 

 negative controls. The following are the results: 



Weak solution of tyrosin (positive control) + 

 Weak solutioi} of tyrosin in milk (positive control) -f- • 

 Milk alone (negative control) — 

 Milk cultures, all -- 



