178 STATE BOARD OF AGRICULTURE. 



The above extract of tyrosinase was so weak, however, that httle reliance 

 was placed on the results. Accordingly the cultures were held for a few weeks 

 longer while an attempt was made to obtain some mushrooms from which a 

 more active extract of tyrosinase could be prepared. This was difficult to 

 do in mid-winter since only dried specimens of the mushrooms could be ob- 

 tained. Finally a glycerine extract of Russula densifolia was prepared which 

 was fairly active but which also blackened slightly without the addition of 

 tyrosin, indicating there was a trace of tyrosin present in the mushroom. 

 The following results were obtained: (ad= indicating that the color was no 

 darker than the negative controls while the + signs indicate the degrees of 

 .color obtained.) 



Negative control (water) ± 

 Negative control (milk) dz 



Positive control (tyrosin dissolved in Avater) -\ — | — | — \- 



Positive control (tyrosin dissolved in milk) + + + + 



Cult. B. A. + + + + Cult. Pv. A. + + + + 



Cult. B. B. ± (negative) Cult. Pv. B. + + + 



Cult. B. C. -f -F + + Cult. Pv. C. + + + 



Cult. B. D. + + Cult. Pv. D. + + + + 



Cult. D. A. + + + + Cult. Sp. A. + + 



Cult. D. B. + + + Cult. Merck. A. + + + + 



Cult. D. C. -F Cult. Merck. B. + + + + 



Cult. Merck. C. + 



In four of the cultures— " Sp. A.," "Pv. A.," "Pv. B.," and "Pv. C."— 

 the production of tyrosin was great enough to be observed by the naked 

 eye as fine white tufts of silky crystals in the bottom of the flasks. Some of 

 these were separated out mechanically and were proved to be tyrosin by 

 microscopic and chemical tests (Moerner's Reagent, Folin and Denis' Re- 

 agent and Piria's sulphuric acid test). 



There is no doubt that all of these organisms, except "B. B.," "D. C." 

 and "Merck C." are capable of producing tyrosin from casein. Some of 

 them also produce typtophane. The few discrepancies in the results obtained 

 by the biochemical test should be disregarded because of the fact that, as 

 tyrosin is nearly insoluble, it is very easy to obtain a negative result even 

 when there is enough t3Tosin present to see it with the naked eye. 



While these experiments were in progress two further samples of pepsin 

 were received from the same company with a request for a bacteriological 

 analysis. Mr. Keyt, a student assistant, plated out the samples and ob- 

 tained counts of 620 per gram from one of the pepsins and 160 per gram from 

 the other. 



It is interesting to note from the above that commercial pspsins may be 

 heavily contaminated with organisms which can decompose protein, splitting 

 them to amino acids. Even when special attsmpts were pr:3umably being 

 made to produce a sterile product, there were still undesirable organisms 

 present though in small numbers. 



II. Examination of a brand of filled evaporated milk for the cause of a hitter 

 flavor. — A firm manufacturing filled evaporated milk requested us to ascer- 

 tain the cause of a bitter flavor in the product, which was put up in cans and 

 was supposed to be sterile. They stated that their own bacteriologists had 

 pronounced the product contaminated with heat resistant organisms. They 

 also stated that the trouble appeared rarely and then only in the baby size. 



