IOWA ACADEMY OF SCIENCES. 91 



others have studied the flora of cheese. All find an abundance of bacteria present. 

 They are rerobic and aniombic. Bacteria are very important to the cheeseniaker. 

 Cheese without bacteria cannot be made. First of all, in most cases it is necessary 

 for the milk to sour so that the whey can be removed. Af^ain it must pass through 

 a stage of ripening before it becomes digestible. The species differ for different 

 kinds of cheese, and there are several kinds connected with every cheese. As in 

 milk, cheese has its enemies in bacteria. Some that cause abnormal npening, or 

 color it black, yellow or red.'" Bacteria always play an important part in the 

 formation of Koumiss. Kefir and other alcoholic fermentation* come from Asia 

 and Europe. Mix has shown that forms of alcoholic fermentation of milk occur in 

 North America. The so-called Kephir grains contain the organisms essential for 

 fermented drink Kephir. Yeasts and bacteria have been found. Kern'" considers 

 that Diaspora caucasica causes the fermentation. Recent investigations leave 

 much doubt in regard to its being an organism at all. Little is known concerning 

 Koumiss, but that it is caused by some living ferment cannot be doubted. The 

 nomadic tribes of Tartary prepared it from mares' milk, which readily undergoes 

 alcoholic fermentation, Ordinarily it is prepared by adding a little Koumiss or 

 sour, to the sweet milk. 



Another interesting group of organisms found in milk are the slime forming 

 bacteria. These organisms cause milk to become very viscous and 'ropy.' It can 

 be drawn out in long threads. This slime, a product from the cell- wall, is anal- 

 agous to the zoogloea formation in certain bacteria, and comes from the decom- 

 position of sugar. Some of the species that can cause this are Bacillus mesenter- 

 icus, B. viscoisus, and Micrococcus discosus, Bechamp the so-called Frog- 

 spawn {Leuconostoc mesenterioides) found in molasses, etc. The species are not 

 uncommon. 



Lastly I should mention that bacteria are indispensable to housewives in the 

 making of bread. In this case they are aided very materially by yeasts. Miss 

 Golden"' has made a contribution to our knowledge of this process and the role 

 bacteria play in bread-making. Miss Golden concludes that bacteria as well as 

 yeast separately can cause bread to rise but that both usually act together. Laur- 

 ent'** believes that his BaciUius panificans causes the rising of bread besides 

 forming lactic, acetic, and butyric acids. 



In conclusion, you will pardon me for having consumed so much of your time. 

 In fact as I look over this question I cannot but think that the subject is so vast 

 that one address will scarcely touch upon the many important problems. The sub- 

 ject of ptomaines and various products of bacteria, disinfection and other points 

 have not been touched up, except incidentally. I venture to say that any one of 

 the topics taken up in this address might very appropriately have consumed the 

 entire time. I shall, however, feel repaid in preparation of this paper if some of 

 the popular notions concerning these baneful and useful organisms, stand cor- 

 rected. 



ii*Adametz ueber die ursachen und erreger der abnormalen Relfungsvorgange beim 

 Ka2se pp. 70. with 6 illustrations. Bremen, 1893. M. Helnsius nachfolger. 



"^Contributions from the Cryptogamic Laboratory, Harvard University. 



"SUeber ein Milchterment, Bot. Zietung, 1882, p. 264. 



"9Bot. Gazette. Vol. XV, p. 204. 



"8See Centralblatt f. Bakt. und Parasitenkunde, 1887, p. 504. 



