DISEASES OF SHEEP 513 



these nodules become confluent, forming large, diffuse, fissured scabs 

 around the margin of both lips, down on the chin, or up on the nose, 

 or both, in which case the whole muzzle is affected. The removal of 

 these scabs exposes either a purplish-red, easily bleeding surface, or 

 a pitted, yellowish-white ulcer covered with pus, some of which will 

 also be found attached to the under surface of the removed crust. In 

 very extensive lesions there may be sufficient pus so that a small 

 quantity will exude from beneath the crust on pressure. In a few 

 cases the disease spreads to the mucous membrane of the mouth, 

 forming small ulcers or fungoid elevations, soft, red, and of a spongy 

 consistence. In both corners of the mouth there are usually present 

 small yellowish necrotic areas which are generally the last to heal. 

 A typical, offensive odor, similar to that of Limburg cheese, is given 

 off from the infected parts. 



In some of the most extensive cases of this form there is a loss of 

 tissue due to ulceration, resembling^that seen in the lip-and-leg form. 

 In these lesions the active, vegetative filaments will be found pene- 

 trating the healthy tissue. In unmolested cases, except probably the 

 more extensive of this form of the disease, the crusts remain intact 

 until the lesions are fully healed, when they drop off, leaving a clean, 

 healthy looking surface. In such lesions the quiescent coccoid and 

 bacillary forms of the bacillus will predominate, while only an oc- 

 casional short filament will be observed. 



We have positive proof of numerous cases of the malignant type 

 of lip-and-leg ulceration developing from the lesions in sore-mouth 

 lambs. 



CAUSE OF THE DISEASE. 



There can be little doubt that the disease is primarily the result 

 of abrasions of the skin and other tissues, allowing the access of the 

 causal organism. The latter may be a natural habitant of certain 

 localities or of certain vegetation. One factor that is predisposing in 

 these cases is a prolonged drought which renders the feed scarce, in- 

 ducing the sheep to browse on thistles and roughage which cause the 

 necessary abrasions. In fact, it is frequently noted that after rains, 

 with the consequent growth of luxuriant feed, the disease becomes 

 checked and affected animals rapidly recover. There seems to be 

 some connection between dry weather, or rather very dry feed, and 

 the appearance of the disease. While there are many factors 

 in dry herbage liable to produce slight abrasions of the lips nec- 

 essary for the entrance of germs, in succulent pastures there are few 

 or none. However, such abrasions by themselves will not produce 

 the disease, but when they become infected with the germs of necro- 

 sis, lip-and-leg ulceration follows. The necrosis bacillus, which is 

 very widely distributed by nature, will not enter a healthy tissue, 

 requiring, as it does, an abrasion, puncture, or wound through which 

 to gain access. Of course a spine or prickle, if contaminated with 

 these germs at the time of puncture, will act as a direct agent of 

 introduction. 



There are several conditions which are responsible as predispos- 

 ing factors for infection by this organism : 



