160 MASS. EXPERIMENT STATION BULLETIN 167. 



Summary of Table I. 

 Medium I. 

 Lots A and B. — Table I. indicates an increase in both Ph and the amount of 

 the formol titrating nitrogen as the treatment continued. The decrease in the 

 hydrogen ion concentration may be due to the volatility of an organic acid, and 

 the increase of the formol titrating nitrogen is apparently caused by hydrolysis 

 in the course of treatment. These changes became constant after the media were 

 boiled for forty-five minutes or longer. On the other hand, there is a marked 

 difference between lots A and B from the standpoint of the hydrogen ion con- 

 centration and the amount of the formol titrating nitrogen; especially, the amount 

 of the formol titrating nitrogen in lot A is nmch greater than in lot B. This is 

 very interesting, because it indicates the possible existence of such variation in 

 the same lot of chopped lean beef. 



Medium II. 



Lots A, B and C. ■ — The same changes occurred in each lot as in Medium I., 

 namely, a decrease of hydrogen ion concentration and an increase of the formol 

 titrating nitrogen. The variations among the lots A, B and C were slight, how- 

 ever. This indicates that Liebig's meat extract from different jars gives fairly 

 uniform results. 



Medium III. 



Lots A and B. — The same changes were observed in this medium a? in Medium 

 II. It is also seen that the properties of the medium became almost constant 

 after it was autoclaved. Both lots A and B agree with each other very closelj^ 

 Significantly the rate of increase of the formol titrating nitrogen is very marked 

 in this medium. 



Medium IV. 



Lots A, B and C. ■ — The same phenomena were observed in this medium as in 

 the others. After their properties became uniform there was very slight varia- 

 tion among them. 



Biologic Test of Medium IV. — After it was found that Medium IV. gave 

 uniform results chemically and physically, an approximate biologic test was 

 applied macroscopicaily in the following manner. Two test tubes for each lot 

 were prepared and filled with 10 cubic centimeters of the medium, respectively. 

 They were then sterilized. One test tube from each lot was kept for control, and 

 the other was inoculated with B. sublilis. They were placed in the incubator at 

 37° C, and an observation was made each day for six successive days. 



Table II. — Growth of B. Si(btilis in Mediuvi IV 



— indicates no growth. 

 +indicates slight growth. 



+-r- indicates strong growth. 

 -|-+-|- indicates abundant growth. 



