378 MILK AND MILK PRODUCTS 
The number of bacteria is probably not proportional to the age of the 
milk. 
Temperature. The effect of temperature on the bacteria in milk 
has received attention from several standpoints. No single extensive 
piece of work has been carried out on this subject and consequently our 
knowledge must come from the various separate pieces of work. Lux- 
wolda (1911) found that milk kept at low temperatures contained an 
enormous number of bacteria. These did not cause an acid reaction 
in the milk but the changes were regarded as more dangerous than if 
the acid bacteria had been present. At 20° C. lactic acid bacteria 
appeared and exerted a restraining action on the other forms. ‘This 
restraining action was steadily diminished as the temperature was 
lowered. Reed and Reynolds (1916) inoculated sterile flasks of milk 
with pure cultures and incubated them at four different temperatures 
for six weeks. The results are shown in Table XL. 
TABLE XL 
EFFECT OF AGE AND TEMPERATURE ON BACTERIAL GROWTH IN 
MILK 
(After Reed and Reynolds) _ 
Acre IN Days, or MitkK Kept aT Vartous TEMPERA- 
TURES, WHICH GAVE Maximum Counts on Nvrrient 
AGAR. 
Name of Organism. —~ a 
Incubator, Room, Water Tank,| Cold Stor- 
35° C. 15-28° C. 13°C age, -—1°C. 
Bacterium lactis acidi............ 1 3 5 3 
Sarcina lutea... .. 2... ee eee ee eee 1 42 42 21 
Bacillus coli... .... cee ee eee 3 5 5 2 
Bacillus eyanogenes.............. 2 21 4 42 
Bacillus proteus vulgaris......... 2 2 4 3 
Bacillus aerogenes..............- 3 5 42 3 
Bacillus fluorescens liquefaciens. . . 2 5 42 3 
Bacillus puditum................ 3 4 5 21 
Microspira tyrogena............. 3 21 42 42 
Bacillus subtilis.............000. 3 42, 42, 21 
Micrococcus citricus............. 21 5 4 4. 
Oidium lactis ...........00 eee 42 42 5 42 
Bacillus prodigiosus.............. 3 42 42 42 
‘Heenan enter pena RNEASY TSN NRErHNRtRTtin mir rinsnn — vagaraafiny trmrrAAnfritsty suet qihreiny th memrammatemmnanivemtetietin tm Hhhtennrneunttninnneteme mtcanemitthideeennremnt in rsbisnisvntneane “ 
Reed, H S and Reynolds, R. R. Some effects of temperature upon the growth and activi 
of bacteria in mailk, Virgima Ag. Exp, Sta, Bull. (Tech.), 10, 1916. ctvaty 
Conn and his co-worker Esten (1902, 1908, 1904) gave much atten- 
tion to this subject. Their work was some of the earliest on this sub- 
ject. In general, they found that at 20° G. the ordinary lactie acid 
