154 JOHNE^S DISEASE 



fed with pure cultures of the bacillus, gave entirely 

 negative results. In all cases single inoculations were 

 made, and the animals were examined in periods vary- 

 ing from two months to two years after the inoculation. 

 In one rabbit, inoculated intraperitoneally, a caseous 

 nodule about the size of a large pea was found em- 

 bedded in the intestinal wall ; the nodule involved the 

 peritoneal and muscular layers, and although a few 

 acid-fast bacilli were found microscopically, they could 

 not be recovered in culture, and were probably dead. 

 The result must be considered negative. 



More recently C. C. Twort and T. Craig have 

 investigated the effect on rabbits and hens of massive 

 doses of Johne's bacillus, not so much with the idea of 

 reproducing the typical disease as with the intention 

 of studying the toxic effects of the bacillus in com- 

 parison with other members of the acid-fast group, and 

 the mechanism of the immunity of these small animals. 

 The results detailed below refer to the experiments of 

 these workers, and if one takes into account the size 

 of the doses, they demonstrate the relatively low 

 toxicity of Johne's bacillus. 



The Intravenous Inoculation of Rabbits. — The in- 

 oculation of a single dose of 30 to 120 milligrammes of 

 Johne's bacillus produces apparently no ill-effect on 

 the animals, which eat well and show no loss of weight, 

 while in a young animal the normal growth is unim- 

 paired. There is no immediate or subsequent rise of 

 temperature, or, at the most, a rise of 0*5° F. on the day 

 following the injection. If a second injection is made 

 three to five days later, there is again apparently no 

 ill-effect, except, perhaps, some slight loss of appetite 

 for a day or two, and the temperature remains prac- 

 tically constant. In a large number of animals inocu- 

 lated with Johne's bacillus the rise of temperature 



