414 The Diseases of Animals 



day and gradually increasing the time as the animals 

 become accustomed to the change of food. It is prob- 

 able that several diseases are often confused under 

 the name "cornstalk disease." 



"big jaw," OB ACTINOMYCOSIS OP CATTLE 



This disease is also called "lump jaw," and in some 

 localities the bunches, or tumors, are called wens. 

 Actinomycosis is due to a vegetable organism that gains 

 entrance to the tissues, and, growing, produces a lump 

 or tumor, which may grow to a large size. It usually 

 occurs in the region of the head or neck. Figs. 57, 58. 



The first symptom is a slight swelling, such as might 

 come from an injury, usually appearing on the face or 

 lower jaw. In most cases the enlargement is due to the 

 bulging outward of the bone, the fungus causing the 

 disease having gotten inside the bone by working its 

 way along the roots of the teeth. As the disease pro- 

 gresses, the tumor becomes larger and finally breaks, dis- 

 charging a thick, sticky pus, but it does not diminish 

 much in size as a result of this discharge. It may heal 

 temporarily, but it gradually increases in size and, later, 

 breaks again. The teeth in the affected part often be- 

 come ulcerated and the jaw sore, so that the animal is 

 unable to chew its food properly. Actinomycosis is 

 rarely seen in calves. 



If a drop of the pus from an actinomycotic tumor is 

 spread out thinly on a piece of glass, minute yellow 

 specks can be seen with the naked eye. If these specks 

 are placed under a microscope and slightly flattened, 



