41 



time of their inoculation were quite healthy. Four out of the six became 

 diseased, while the rest showed only passing symptoms and disturbances. 



A second series of experiments was carried on with roup cultures which 

 had been passed through two pigeons. The chickens concerned in these ex- 

 periments are No. 34-39 and 42-45- One of them, i.e., fowl 39, was infected 

 with a culture which had been grown on artificial media for three weeks, after 

 isolation from the second pigeon ; in this case the bird was only very slightly 

 affected. In all the other fowls, the cultures were used as soon as possible 

 after isolation from the last pigeon. All reacted with pronounced symptoms 

 comparable to those of a natural attack of roup. Two cases ended in death 

 in five and thirty-three days respectively. Two lead to chronic loss of flesh 

 and were anaemic. Fowl 2,(> was killed after a bad attack which lasted 22 days. 

 The other diseased fowls recovered in 3 or 4 weeks. 



The virulence of the roup bacillus might be made even more virulent by 

 passage through a longer series of pigeons. 



The pigeons themselves can be infected with the roup bacillus and show 

 symptoms identical with those in chickens, but we seldom hear (A pigeons 

 sufifering from roup under natural conditions, but they may become diseased 

 as has been proven by these experiments. Very probably, they are more 

 resistant against the natural channels of infection, being kept in relatively 

 healthier localities than the average flock of farm chickens. 



Fowl No. 27 could not be infected even with large quantities of the viru- 

 lent cultures of the roup bacillus. It seemed to possess a natural immunity 

 to roup. 



Subcutaneous injections of 1-8 c.c. to H c.c. cultures of the roup bacillus 

 caused only slight disturbances of the general condition. The skin was often 

 colored green about 24 hours after the injection, and occasionally small solid 

 tumors (solid pus) formed. Larger quantities (2-5 c.c.) of the culture caused 

 large tumors, which were hard and painful at the beginning ; later, 

 a hard solid, smooth or uneven, tumor formed in the depth (similar to the ef- 

 fect on the eye-lids), when the symptoms o.f acute inflammation disappeared, the 

 solid tumor remained as a foreign body for months ; and the fowl lost flesh, 

 became thinner and thinner, anaemic, and often died in from two to six months 

 after inoculation, or recovered very slowly. The solid tumors are nothing but 

 a mass of solid cheesy pus (see fowl 40 and pigeon 5). 



Injected into the muscles, the roup bacillus causes extended necrosis of the 

 tissue, which smelt offensively. 



In the pleura and peritoneum, putrid inflammations are produced, from which 

 the fowls may recover, but often die after a chronic disease (anaemia) lasting 

 from 2 to 12 weeks. 



Two chickens and two pigeons were fed with cultures of the roup bacillus 

 mixed with their food, and no bad results followed. 



Fowls and pigeons once infected with roup could be infected a second time 

 after recovery from the first attack. Birds which had suffered from a natural 

 attack of the disease and then recovered, also became again infected by the 

 inoculation of the Roup bacillus ; and finally serum from naturally or artificially 



