170 Canadian Record of Science. 



Milk is sometimes supplied to dealers in glass bottles. 

 Now unless these bottles are most scrupulously cleaned 

 after using, before being refilled, we have all the conditions, 

 so far as we know them, most favorable to the develop- 

 ment of this poison. 



From what has been said already it will be evident that 

 the decomposition of milk may take place in several 

 different ways. The usual way is what is called the 

 "lactic fermentation." In this form the decomposition 

 appears to start in the milk sugar, part of which becomes 

 converted into lactic acid and the milk turns sour. The 

 formation of this lactic acid, coagulates the casein and the 

 milk curdles. Then the casein and albumen molecules 

 break up into simpler molecules. Carbon dioxide, ammonia 

 and other bodies are formed. Carbon dioxide is con- 

 tinuously evolved from milk during decomposition, but 

 only in a very moderate quantity. 



This form of decomposition has been shown to be due to 

 a micro-organism — the Bacterium lacti's 1 — minute bodies in 

 the form of beads strung together or in that of threads. 

 They grow and increase in number by a process of fission — 

 that is one of the minute cells, divides, so as to form two 

 individuals, and these in their turn divide again. The 

 bacteria feed upon the sugar and albuminoids of the milk, 

 and thus in some way bring about that peculiar form of 

 decomposition which is known as the lactic fermentation. 



The presence of acid checks the lactic fermentation, so 

 that under natural conditions only part of the sugar is 

 converted into lactic acid. But if chalk is added to 

 neutralize the acid as it is formed, the whole of the sugar 

 may be changed into lactic acid. 



The alcoholic fermentation which takes place in koumiss 

 and kephir is also due to minute fungus, the Saccharomyces 

 cerevisice, or ordinary beer yeast — the same plant which 

 causes the fermentation of beer, wine and the wort from 

 which spirits are distilled. It is a plant similar somewhat 

 in appearance to the B. lactis, but much larger. 



Sometimes another kind of fermentation occurs — the 

 butyric. The product in this case is butyric acid, and it 



