42 JOURNAL OF THE [March, 



called bacteria. The existence of these organisms in leaven 

 and dough had been pointed out several times without any one 

 ever dreaming of according them any very important role ; but 

 such was not the case with quite a small form found in leaven 

 by Mr. Engel, who had no hesitation in attributing to it the 

 phenomenon of panary fermentation. This was in 1872. At 

 this epoch there was very little talk of the chemical action pro- 

 duced by bacteria, and a somewhat peculiar circumstance was 

 adduced in favor of yeasts. It appears that for many centuries 

 it has been customary in some places to add a little brewer's 

 yeast to dough, and, at present, bread made in this manner is 

 extensively eaten in those countries where beer is the principal 

 beverage. What role must be attributed to brewer's yeast in 

 the preparation of bread ? Have we here an alcoholic ferment 

 as in the brewer's mash-tub ? This is a very delicate question, 

 and one which would require an excursion into the domains of 

 chemistry for an answer. 



Let us now pass to something that is more directly connected 

 with the subject of this paper. 



Bacillus panificans. — Let us make some dough with any sam- 

 ple of flour whatever, and expose it for a few hours to a temper- 

 ature of 35°. With an amplification of from 400 to 500 diam- 

 eters, the microscope will show us the presence of starch and 

 gluten, and, here and there, of small, slender rods, which are 

 six times their width in length, and which are movable in the 

 water in which the preparation was made. We have before us 

 a bacterium of the type Bacillus. In order to facilitate the dis- 

 tinction of the micro-organisms in dough, it is well to employ a 

 drop of a solution of iodine, or to color the bacilli by means of 

 an aqueous solution of methyl violet or of fuchsine. 



These bacilli are met with in leaven and dough of very di- 

 verse origin, and no sample of either has been examined which 

 does not contain them. Some persons, while admitting that 

 these organisms are dispersed over the entire earth, may never- 

 theless deny their specific unity ; but Dr. Koch's studies have 

 fortunately furnished us with a sufficiently sure means of char- 

 acterizing any species of bacterium. For this purpose, a bit of 

 dough is intimately mixed with a little water freed from germs 

 by the Chamberland filter, or by repeated boiling. A drop of 

 the liquid is added to a tube of gelatinized and peptonized 



