64 IOWA ACADEMY OF SCIENCES. 



SOME EXPERIMENTS FOR THE PURPOSE OF DETERMINING THE 

 ACTIVE PRINCIPLES OF BREAD MAKING. 



MINNIE HOWE, 

 (ABSTRACT.) 



This paper described a series of experiments made by the author at the Iowa 

 State University during the winter and spring of 1891, together with their results. 



The problem was to seperate the bacteriam, Bacillus subtiUs, and the yeast plant, 

 Saccharomyces cereviske, found together in ordinary soft yeast, to obtain pure 

 cultures of each, and to determine the part each played in bread making. 



It was found that bread made of sterilized flour and raised with the pure Bacillus 

 culture was light, but not as spongy as ordin ary bread, sweet, close-grained, rather 

 dark colored, smelling and tasting much like " salt-risen " bread. 



Bread raised with the pure yeast culture under exactly the same conditions as 

 the first was somewhat light, sweet, not so fine grained nor as light as either ordi- 

 nary bread or that made with bacteria. It had a peculiar, insipid odor unlike 

 either of the other kinds, and was tasteless, as if made out of sawdust. 



The results of these experiments seem to show that neither the yeast plant nor 

 the Bacillus alone will make as good bread as both together; that either without 

 the other will produce alcoholic fermentation and cause the bread to rise; that the 

 Bacillus is rather more efficient alone than the yeast. No one set of experiments, 

 however, can be regarded as conclusive. 



ABORIGINAL ROCK-MORTARS. 



BY H. L. BRUNER. 



A few notes by the writer, under the above title, were published in the American 

 Anthropologist for October, 1891. 



These "mortars", excavated in rock in situ, are located on the east slope of the 

 Franklin Mountains, about eleven miles north of El Paso, Texas, and near the 

 mouth of the ''House Canon." 



In the canon, about three-fourths of a mile above the excavations, is a spring of 

 excellent water. To the eastward is a gradual slope toward the mesa, which is 

 perhaps three hundred feet lower. Within a few steps of the excavations is a trail 

 leading northward to another spring, and thence westward over the range. 



