114 Minnesota Plant Life. 



Fermented milk. Together with yeasts, there are lactic-acid 

 fermenting bacteria employed in the manufacture of the fer- 

 mented liquor made in the region of the Caucasus from goat's 

 milk and known as kephir. In Minnesota, while the souring 

 of milk is a natural phenomenon which has been observed by all, 

 I am not aware that fermented milks are commonly produced. 



Milk-curdling bacteria. Different from the souring of milk 

 is its curdling, which takes place when rennet is placed in it. 

 Rennet types of fermentation may be initiated by bacteria, al- 

 though a more common source of rennet is the calf's stomach. 



Souring of wine, beer, bread and ensilage. Lactic types of 

 bacteria are not only common in milk but in wines and beers, 

 so that in the brewing industry some sorts of souring which beer 

 undergoes arise from lactic-acid germs, while others are due to 

 vinegar-fermentation. The souring of bread l)y lactic fermen- 

 tation is not unknown and in the souring of ensilage and fodder 

 the activity of these bacterja is ordinary. 



Vinegar-bacteria. Still another type of fermentation is the 

 vinegar-fermentation by which sugars, such as those of sweet 

 cider, are converted into acetic acid, commonly known as vine- 

 gar. In the manufacture of vinegar the activity of these bac- 

 teria is utilized and upon their growth depends every art in 

 which vinegar is emi)loyed. Acetic acid ferments may originate 

 also in beers and wines, in breads, and sometimes in fruit-jellies. 

 The bacteria which produce the ferments are not all of the same 

 sort but arc of several diiTerent kinds. 



Antiseptic surgery. One very important special technical 

 process is largely dependent upon the control of various fermen- 

 tive bacteria, namely, antiseptic surgery. The precautions which 

 the surgeons take in entering upon an imi)ortant operation, are 

 intended to prevent the ingress of putrifactive or other fermen- 

 tive bacteria into the wound through the operation. Hence the 

 carbolic-acid-spray, the heating of the knives, lint, bandages and 

 sponges, the dress devised to catch as little dust as possible, the 

 cleanliness of all utensils, and the fro(|ucnt ilhunination of the 

 operating room in good hospitals by sunlight. W ith the suc- 

 cess of antiseptic methods it has been discoxered that pus or 

 "matter," as it is i)opularly termed, is not an unaxoidable con- 

 comitant of woiuid-hcaling. Wounds not of siu'gical origin. 



