NEw YorRK AGRICULTURAL EXPERIMENT STATION. 59 
The plan of denct ng the different media by numbers has been 
found useful in both laboratory work and in records and will be 
followed in this publication. In this media record the digit signifies 
the form of medium as bouillon, gelatin or agar. The first decimal 
place gives the kind of.sugar employed and the second decimal place 
is left for other variations. Thus 2.00 signifies the plain peptone 
gelatin, 2.30 the same medium with the addition of cane sugar while 
2.31 is used for the latter medium when made without adjusting the 
reaction. 
We have followed the suggestions of the committee on standard 
methods of the American Public Health Association’® as reported in 
1904 in the preparation of our media except that we have uniformly 
used Liebig’s beef extract and sodium chloride and unless otherwise 
stated have titrated to a standard reaction of + 1.5 per ct., that is 
of 15 cc. normal acid to the litre. Titrations were made with hot 
solutions using N/1o sodium hydroxide and phenolphthalein. 
Medium 2.22.— This is our plain peptone gelatin. It was rarely 
employed except to test liquefaction in the work of classification. 
Medium 2.02.— This differed from the above medium only in its 
reaction, being made neutral. We used it for plating out cheese 
samples when studying the liquefiers and non-acid-producing 
bacteria. | 
Medium 2.22.— This was the principal medium used for both 
quantitative and differential study. In preparing plates with 
meditim 2.22 each plate received 1 cc. of the cheese emulsion, I cc. 
of the litmus solution and 8 cc. of the whey gelatin. The plate ac- 
cordingly contained approximately I1 per ct. gelatin. 
Preparation of the whey Three hundred cc. of sour milk was 
mixed with to litres of fresh, skimmed milk and the mass coagu- 
lated with 5 cc. of rennet extract. The coagulum was cut up finely 
and allowed to stand 1 hour. After being drained off and sterilized 
the whey was ready for use. 
Preparation of the litmus solution— One hundred grams of dry 
litmus cubes was added to 500 cc. of distilled water. This was held 
24 hours at 37° C. after which it was filtered and the reaction of 
the filtrate adjusted to + 1.5 per ct. after the method suggested by 
Conn & Esten.!’ This litmus solution was sterilized in test tubes 
for 30 minutes in the steamer on three successive days. 
* Report of the Committee on Standard Methods of Water Analysis to 
the laboratory section of the Amer. Pub. Health Asso. Journal of Infectious 
Diseases. Supplement No. 1, May, 1905. 
* See note 2. 
