142 REPORT OF THE CHEMIST OF THE 
9. The effect of carbonating milk upon organisms other than 
lactic, under the conditions of our work, has not yet been studied. 
i INTRODUCTION. 
In making a study of the chemical changes that take place 
in cows’ milk when made into kumiss, we have observed that 
the product, if properly made and kept, remains for a much 
longer time without souring than in the case of ordinary milk 
kept under the same conditions. In the preparation of kumiss, 
conditions not present in normal milk are introduced; and the 
inquiry was naturally suggested as to what particular factor was 
responsible for the delay of formation of lacti¢ acid in kumiss. 
Our method of preparing kumiss, briefly outlined, is to add 
cane sugar (sucrose) and yeast to fresh milk, keep the mixture 
at about 100° F. until gas begins to form and then to bottle 
and keep at 35°-45° F. In the course of one or two days some 
alcohol is formed and enough carbon dioxide to cause consider- 
able pressure. It is thus seen that, in the preparation of kumiss, 
the following factors are present, most of which do not exist 
in normal milk: (1) Sucrose, (2) yeast, (3) heat, (4) products 
of fermentation, especially (a) carbon dioxide and (b) alcohol. 
In order to ascertain which of these factors might be the cause 
of the delay in the lactic fermentation in kumiss, we made a 
special experimental study of the different conditions involved. 
INVESTIGATION. 
FIRST EXPERIMENT: INFLUENCE OF DIFFERENT FACTORS IN RETARD- 
ING LACTIC FERMENTATION IN KUMISS. 
In each of several bottles we placed about two liters of fresh, 
separator skim-milk and heated to 100° F. Four fresh yeast 
cakes (Fleischmann’s) were rubbed up in 500 cc. of milk. The 
milk in the different bottles was treated in the manner indicated 
below. 
ree TEKS 
2. Milk + 20 grams of sucrose. 
3. Milk -+ 100 cc. of yeast solution. 
4. Milk + 100 cc. of yeast solution-++ 5 grams of sucrose. 
4a. Milk + 100 cc. of yeast solution-+10 grams of sucrose. 
4b. Milk -+ 100 cc. of yeast solution + 20 grams of sucrose. | 
4c. Milk + 100 cc. of yeast solution-++ 40 grams of sucrose, 
