IOWA ACADEMY OF SCIENCES. 169 



that it is not often recognized because the conditions of keeping 

 are such that it does not develop. It also shows why the 

 trouble appears only during the hot weather of summer. 



The writer has been asked why this trouble is not more 

 general. The answer is in the facts given regarding the effect 

 of temperature, and it is also probable that in many cases 

 such fermentation starts to develop and as soon as the first 

 indication, the disagreeable taste and odor appears, the bread 

 is destroyed and the final stringy condition is not seen at all. 



The condition of the bread regarding moisture seems to be 

 an important factor in developing the fermentation. The 

 more moisture present in the bread, the more rapidly the fer- 

 mentation develops, and in this way the conditions of making 

 have some influence. 



THE BACILLI CAUSING THE FERMENTATION. 



A large number of Petri dish agar cultures were made from 

 different samples of bread, and from particular samples at 

 different stages of development. In ail but one case the com- 

 mon potato bacillus. Bacillus mesentericus vulgatus, was the most 

 common organism present. With a single exception these sam- 

 ples also contained another species in many respects resem- 

 bling the potato bacillus, and while differiag in some miaor 

 respects from the original description, it agreed in the essen- 

 tial points and was considered to be Bacillus Uodenno, 

 (Loefaer).'''^ The case which did not show the B. liodermoss 

 appeared to contain a mixture of Bacillus mesentericus vulgatus 

 and Bacillus suhtilis. One sample apparently contained a pure 

 culture of Bacillus liodermos. This sample showed little color 

 but great viscosity. Experiments showed that either the potato 

 bacillus or B. liodermos can produce this slimy decomposition 

 in sterile bread but a much more pronounced yellow color is 

 produced under the influence oi the potato bacillus. A culture 

 of the potato bacillus was secured from partly sterilized potato 

 and this was found to give the same result as theculture of the 

 same organism secured from the spoiled bread. It is impos- 

 sible to estimate to what extent each species took part in pro- 

 ducing the slimy decomposition. The potato bacillus appeared 

 to be more active during the first part of the process, while 

 later almost pure cultures of B. liodermos would be secured in 

 some cases. 



♦BerUner kUn. Wochenschr, 1887, p. 630. Also Sternberg, Manual of Bacteriology, 

 p. 680. 



