THE BACILLUS FOR SMALL ANIMALS 167 



by intravenous inoculation of Johne's bacillus, B. phlei^ 

 or the human tubercle bacillus. Five to ten milli- 

 grammes of any of these bacilli often produce rapid 

 death of the animal if inoculated intravenously, while 

 in many cases a previous high rise of temperature is 

 noted. This rise of temperature is usually preceded 

 by a well-marked fall, which occurs during the first 

 hour or two following the injection. When the inocu- 

 lation is made subcutaneously, the temperature often 

 rises but httle, and the experiment never terminates 

 fatall3^ It requires no larger dose of dead Johne's 

 bacillus to kill an animal immune to the human tubercle 

 bacillus than it does of the latter to kill an animal 

 immune to Johne's bacillus. The bacillary emulsions 

 have not been accurately titrated to find the minimal 

 fatal dose, and it is, of course, assumed that the dose 

 would be smallest in those cases in which the homolo- 

 gous bacillus is used. Control animals, immunized 

 with emulsified Dorset's ^gg medium to eliminate any 

 effect of the tgg albumin in these reactions, were 

 negative, both as regards the production of a rise in 

 temperature and the death of the animal. 



If mice are inoculated into the peritoneal cavity with 

 dead Johne's bacillus, B. phlei, or the human, avian, or 

 bovine types of tubercle bacilli, the most prominent 

 feature is the more rapid disappearance of the four last- 

 mentioned varieties as compared with Johne's bacillus. 

 It is about a week or more after the injection that the 

 difference is most noticeable. At the same time animals 

 inoculated with Johne's bacillus do not appear to die 

 so frequently as when inoculated with the other bacilli. 



Experiments m vitro on the toxicity of the bacilli to 

 guinea-pig's leucocytes are also interesting. The leu- 

 cocytes can be obtained in the usual way by the in- 

 traperitoneal injection of Mellin's Food,| or similar 



