136 BACTERIA. 



are straight, somewhat rounded at the extremities, single, or 

 arranged in short chains of three or four elements ; if placed 

 in a nutrient medium similar to that in which yeast grows, 

 they are reproduced by a process of vegetative division, 

 especially if this medium be neutral, or slightly alkaline, and 

 if it be kept at a temperature of 40° C. 



The formula of the process of splitting up is given as first 



CisH„0 6 ^ 2C3H6O3 



I Molecule Glucose 2 Molecules of Lactic Acid 



The two Molecules of Lactic acid are then transformed into 



QHsO. 2CO, 



I Molecule of Butyric Acid 2 Molecules Carbon Dioxide 



2H, 



2 Molecules Hydrogen 

 In the same way two molecules of malic acid are broken up into two of lactic 

 acid and two of carbon dioxide, and the lactic acid is ^ain transformed as 

 above, that is, 2C4H6O5 = 2C3H6O3 + 2COj = C4H80s + 4CO, + 2Ha. 

 This butyric acid formation is only one of a group, and we find that where 

 lactic fermentation is going on in an impure condition propionic acid, 

 CjHsOa, acetic acid, C2H40a, and valerianic acid, CsHkOs, are produced, 

 and glycerine fermented for some time with beer yeast, is split up into pro- 

 pionic acid mixed with formic and acetic acids, giving a kind of compound 

 of putrefaction products. 

 A very ingenious formula is quoted by Schiitzenberger to show how 



the fatty acids are formed from sugar : — (CsHijOe) = 



[C„H.„OJ ^ ( n-2)CH.a p^^^ig j^^y j^g ,g ^f J J y 



Fatty Acid Formic Acid •' 



group, being immediately converted into carbon dioxide and hydrogen. The 

 presence of lime or organic matter appears to modify this process some- 

 what, and to give rise to the formation of secondary v^etable acids. For 

 instance, two molecules of malic acid, 2C4H6OS, break up into succinic acid, 

 C4H6O4, and tartaric acid, 2C4H6O6, and from these are formed, from the 

 tartaric acid the fatty acetic acid, CaH40a + COj + Ha, and from the 

 succinic acid the fatty valerianic acid, carbon dioxide and hydrogen, 



CsH,oOa + 3COa + Ha. 



These transformations have this in common, that they 

 are all brought about by the presence of minute organisms, 

 that the conditions of the development of these organisms 

 are similar to those met with in other fermentation pro- 

 cesses, and that theirs are the principal products formed 

 during the process of putrefactive fermentation, which also 

 in all cases requires the presence of these minute organisms, 

 the spores of which, as we have seen, seem to be everywhere 



