New York AGRICULTURAL EXPERIMENT STATION. 89 
ence of alcohol, volatile fatty acids and gases among the lactic 
acid fermentation products has also been shown by Leichmann,’° 
and acetone by Jacksch.1! The quantity of lactic acid formed 
is dependent, according to Emmerling,’® upon a variety of condi- 
tions, among which the following may be mentioned: The kind 
of organism; the reaction of the material, a neutral reaction being 
favorable; the presence or absence of air, the presence of air fav- 
oring the formation of more of the volatile acids; the conditions of 
nutrition, of temperature and of the presence or absence of certain 
substances. ; 
According to Timpe,'? for example, one of the lactic acid organ- 
isms mentioned by him is checked in its growth by .04 per 
ct. of free lactic acid. However, the growth is not checked, so 
long as there are substances present with which the acid can 
unite. We have such substances in milk. Using as a basis the 
figures given by Soldner,“ the inorganic compounds in 100 grams 
of milk would unite with 0.3938 gram of lactic acid. Timpe 
found that 100 grams of milk-casein neutralize 8.415 grams of 
lactic acid; the milk-casein in 100 grams of milk containing 2.5 
per ct. of casein would therefore neutralize 0.2104 gram of 
lactic acid. Thus the total amount of lactic acid neutralized by 
100 grams of ordinary milk would be 0.604 per ct., and this 
was about the amount of acid found by him in milk that had 
soured in the usual way. In his experience, the maximum amount 
of acid is reached in about 50 hours at ordinary temperatures. 
Our results are somewhat higher than those of Timpe. We find 
as our maximum more lactic acid, which is nearly all formed in 
48 to 72 hours. There will, of course, be a variation in different 
milks dependent upon the amount of casein and inorganic salts, 
other conditions being uniform. Richet'® reports finding 1.6 per 
cent. of lactic acid in sour milk, but this figure appears too 
high and is probably due to some error in determination. Hueppe’® 
Centralbl. Bakt., 16:826 (1894). 
UBerl. Ber., 19:781. 
“Die Zersetzung Stickstofffreien Organischen Substanzen durch Bakterien, 
p. 34. 
Arch, hyg., 18:1 (1893). 
4Tandw. Versuchs.-Stat., 35:351 (1889). 
Compt. rend, 86:550 (1878). 
WM ittheil a. d. Gesundh., 2:309 (1884). 
