BACILLUS BUTYRICUS LIBORIUS. 371 



from its morphological peculiarities in fossil conifers of 

 the coal formation. 



Bacillus butyricus (Liborius). 



Liborius' butyric acid bacillus presents scarcely any 2. Liborius' 

 noticeable difference from the former in its morphological bacSus aC1 

 characters, more especially in its mode of spore forma- 

 tion. Cultivations in solid nutrient media (nutrient 

 agar, or nutrient gelatine, best when grape sugar is 

 added) only succeed when a fairly thick layer is em- 

 ployed, and in this case a superficial zone, about 3 

 cm. in breadth, usually remains free from growth; 

 the organism can also be cultivated in nutrient substrata 

 from which the oxygen has previously been expelled by 

 some other gas. Further, it is of importance not to 

 inoculate the solid gelatine by the puncture method, and 

 thus to form a canal for the air, but to mix the material 

 with liquefied gelatine. In this case whitish, but not 

 sharply defined colonies appear in the course of one or 

 two days, and after 24 hours more become surrounded 

 by a narrow line of liquefaction; the extent of the 

 liquefaction gradually becomes greater, and the whitish 

 mass of the colony sinks to the bottom; ultimately these 

 globules coalesce, and at the same time gas bubbles 

 usually penetrate into the upper part of the gelatine, 

 drive out the oxygen from it, and thus the growth and 

 the liquefaction gradually extend upwards. In nutrient 

 agar the form of the young colonies can be better recog- 

 nised; and it is then seen that their outline is irregular, 

 and even to the naked eye shows a finely branched 

 appearance; under a low power the delicate ramifying 

 threads around the margin of the colony form a very 

 characteristic picture. In the test-tubes containing agar 

 active development of gas also occurs, so that the upper 

 portion appears as if it had been split. These gases 

 have a disagreeable smell, often recalling that of pure 

 butyric acid ; other gases, which probably arise from the 

 simultaneous decomposition of the albumen, are also 

 often present. A more accurate analysis of the fer- 

 mentative products is still wanting. 



