274 AGRICULTURAL BACTERIOLOGY 



crease, the tubercles may become confluent, and form tu- 

 bercular abscesses of varying sizes. Ultimately these ab- 



Fig. 43. Tubercular Omentum 



In a healthy animal this is a smooth thin membrane. Grapes is the term 

 commonly applied to this form of disease by the butcher 



scesses break and discharge their contents into the air- 

 passages of the lungs, the milk-ducts, the bile-ducts, or 

 into some other opening that will enable the bacilli to escape 

 from the body. This condition is known as "open" tuber- 

 culosis, as opposed to the " closed" form where the tubercles 

 do not break down. 



The tubercular animal is a source of danger to others 

 only as it is eliminating the organisms from the body. If 

 the disease has not reached the open stage, or if the lesions 

 are found in parts of the body that have no exterior open- 

 ing, the animal can not be dangerous to others or to the 

 human beings consuming the milk. It is impossible to 



