THE CAUSE OF BLACK DISEASE. 15 



in parts a greyish appearance of commencing necrosis, and in others a pro- 

 nounced inflammatory congestion. They are not of ten actually hsemorrhagic. 

 On section, if the injection has been intramuscular, the injected muscles have 

 an unpleasant but hardly putrefactive odour. Occasionally, there may be a 

 slight amount of exudate in the peritoneal or pleural cavities, but this is not 

 the rule. The spleen, kidneys and liver are congested, and if the disease has 

 lasted twenty-four hours or more there are very occasionally either ill-defined 

 or circumscribed dirty- white areas of commencing necrosis in the latter, about 

 an eighth of an inch in diameter. The stomach and small intestines are as a 

 rule deeply congested, but there is no ulceration. The mucosa is cedematous,. 

 and the contents of the small intestines usually a straw-coloured, clear fluid 

 The pericardium is almost invariably distended with a clear, colourless exudate. 

 As a rule the causal bacteria are confined to the neighbourhood of the site of 

 the inoculation and the subcutaneous exudate of that region, from which they 

 can be recovered in purity, but the further the exudate is from the local 

 lesion, the more scanty become the bacilli. 



Rabbits. 



Small doses of from 0*1 to 0*2 c.c., such as would be sufficient to kill a 

 guinea-pig are not fatal. Very frequently no reaction at all is to be seen. 

 Larger doses, yiz., 0'25 to 0'5 c.c. subcutaneously, usually result in death 

 In a number of instances, even with such increased amounts, death may be 

 delayed until the fortieth hour after injection. Beyond pronounced lameness, 

 there are few clinical symptoms to be observed until near the fatal termina- 

 tion. 



Lesions. There is practically no swelling round the point of inoculation, 

 no cutaneous changes and no gas formation. The subcutaneous tissues in the 

 inoculation area are moderately infiltrated with an exudate, slightly blood- 

 stained near the point of injection, but colourless elsewhere. There is no 

 odour. The superficial muscles in this region are slightly reddened, but there 

 are no haemorrhages. Frequently there is a considerable amount of exudate 

 in the pericardium but no gross lesions elsewhere. The bacilli can be 

 recovered in purity from the inoculation area, but they are not obtainable 

 elsewhere. 



The Fowl. 



Doses of 0-2 c.c. of virulent culture injected intramuscularly are usually 

 fatal, but death does not occur under about forty hours or longer. Here, 

 again, there are few clinical signs of reaction-, the bird looking apparently 

 well until near the end. Death ensues rapidly and quietly once symptoms are 

 manifest. 



Lesions. There are no marked cutaneous changes. The subcutaneous 

 tissues for some distance around the point of inoculation are saturated with 

 the usual inflammatory exudate. Near the point of entrance of the needle, 

 it is slightly blood-tinged, but some distance away, colourless. These tissues 

 also show evidence of necrosis. There is, however, no unusual odour and no 

 gas. The muscles in the inoculated region and for some distance around, 

 hare a greyish-white appearance of commencing necrosis, most pronounced 



