Butyric Acid Bacilli. 



169 



The specific butyric acid bacilli are obligatory anaerobic or 

 facultatively anaerobic, that is they thrive best in the absence of 

 oxygen ; there are, however, aerobic bacteria which are capable of 

 forming butyric acid, for instance several of the above-mentioned 

 peptonizing varieties, the hay and potato bacilli, which without 

 specially attacking the milk sugar, form butyric acid from the 

 products of the split proteids. 



The individual varieties show varying properties toward the different kinds of 

 sugars, as well as toward the formed by-products, as butyl alcohol, isobutyl alcohol, 

 formic acid, acetic acid, propionic acid, valerianic acid, carbonic acid, hydrogen, etc. 



The obligatory butyric acid producers are rods, chains or threads, with either a plump 

 or a slender form; they possess oval or roundish polar or central spores. The bacteria 



Fig. 26. 



Blackleg bacilli. 1 X 1200. 

 (After Friedberger & Frbhner.) 



frequently form so-called clostridium forms, and especially in starch-containing media 

 they take up granulose; therefore certain parts of their body or even the entire bacillus 

 may be stained blue with iodide of potassium. 



The representatives of this group are known to pathologists 

 as producers of blackleg, gaseous phlegmons, malignant edema, 

 bradsot, botulism, and tetanus. These bacilli at times are capable 

 of energetically forming butyric acid, and at other times less in- 

 tensively; at the same time peptonizing ferments (tryptic) are 

 formed, which become active in the absence of acid. 



Generally motile and non-motile forms of butyric acid bacilli 

 are distinguished in milk. The latter form, of the granular Bacillus 

 saccliarobutyricus is considered by Grasberger and Schattenfroh 

 as a developing form of the motile, spore-forming variety which 

 takes up granulose, forms toxins, and attacks lactic acid. 



According to their properties they may be divided into those 

 which form butyric acid principally from certain carbohydrates, 



