BUREAU OF ANIMAL INDUSTRY. 62^ 



and is rarely found covering the entire surface. When a number of 

 successive inoculations are made a week apart the later cultures are 

 quite apt to form membranes after a few days' standing. Thus one 

 microbe forms a membrane very speedily; the other only occasionally, 

 and then quite tardily. 



In these liquid cultures both exhibit, during three or four days 

 after inoculation, very active spontaneous movements. Sometimes 

 masses of five to ten bacteria may be seen moving actively to and fro 

 and at the same tim.e revolving about themselves. 



In the same culture liquid the microbe from Nebraska seemed to 

 grow more vigorously, so that at the end of two or three days the 

 liquid became turbid, and the deposit in the bottom of the tube was 

 very abundant after one or two weeks. 



Both fail to liquefy gelatine. A very slight but significant differ- 

 ence was observed in this medium also. It was found that when line 

 cultures were made on j^lates of gelatine, in order to test the purity 

 of liquid cultures, the microbe from Nebraska failed to develop, while 

 the microbe from the East invariably grew as described in the pre- 

 ceding report. This observation was made so uniformly with every 

 culture that it became later a means of distinguishing the two forms 

 when the cause of this behavior became known. Such lines, after a 

 few days, appeared as an aggregation of mere points under a 1-inch 

 objective, and did not enlarge, or else there was no indication of any 

 growth whatever. 



Later, another quantity of nutrient gelatine was prepared, which, 

 on boiling, threw down a very fine precipitate, uniformly clouding 

 the gelatine. A few drops of acetic acid added to it when liquefied 

 by heat dissolved the precipitate completely. It seemed probable 

 that the precij)itate was some alkaline phosphate or carbonate, and 

 in fact the reaction with litmus paper was more alkaline than Vv'ith 

 the gelatine previously used. In this medium the bacterium from 

 Nebraska grew very well both on plates and in tubes, and the bac- 

 terium from the East grew much better than in the previous prepa- 

 ration of gelatine, thus showing that an alkaline medium is best for 

 the bacterium of hog-cholera, and that the Nebraska variety is by 

 far the more sensitive, and fails to multiply unless the reaction is 

 fairly alkaline. On gelatine plates the colonies are somewhat darker 

 and more coarsely granular when viewed by transmitted light than 

 those which develoj) from the Eastern variety. 



On the surface of beef -infusion peptone aga.r-agar made slightly 

 alkaline with potassium carbonate both bacteria grow very vigor- 

 ously when kept in the incubator at 95° to 100° F. On potato both 

 grow as a dirty straw-colored layer at the ordinary temperature, so 

 as not to be distinguishable. (Plate V, Fig. 3.) 



From the comparative plate cultures and from potato cultures both 

 bacteria, when inoculated into liquid media, showed tlie character- 

 istic difference already mentioned. On the following day one cult- 

 ure would be covered with a membrane, the other not. In milk both 

 multiply without producing any microscopic change. 



This bacterium is likewise killed by a temperature of 58° C, as the 

 following experiment shows: Five tubes containing sterile beef- 

 infusion were inoculated from a liquid culture ten days old, obtained 

 from a mouse. Four of these were placed in a water bath at a tem- 

 perature of 58° C. , and retained there for fifteen, twenty, twenty-five, 

 and thirty minutes respectively. These, with the check-tube, were 

 placed in the incubator. Next morning the check-tube was turbid 



