134 LABORATORY BACTERIOLOGY 
to be affected ; if a rabbit, the lungs are often the first of the 
visceral organs to be attacked. (See pathology for description 
of tissue changes.) 
If it is desired to differentiate. between the human and the 
bovine varieties it is necessary to use rabbits, as the bovine 
variety is generally pathogenic for rabbits and the human 
variety rarely, if ever, is. 
In case tuberculosis is suspected, all or, if too large, a por- 
tion of the lesion should be sent. 
