312 SWINE PRACTICE 



•which the necrotic tissue has sloughed, leaving the intestinal wall 

 relatively thin and inelastic. 



In prolonged cases or the chronic form of this disease the so-called 

 "button ulcer" is of common occiirrence. This lesion occurs when 

 the infection is apparently localized in solitary follicles or Peyer's 

 patches and the inflammatory and necrotic processes extend by con- 

 tinuity, the necrotic tissue remaining intact or accumulating as dirty 

 brown masses with raised margins. Microscopically the surface epi- 

 thelium in the affected areas and the lymphoid tissue are found to 

 be in various stages of degeneration and disintegration. The degen- 

 erated and dead cells commingle with the coagulated inflammatory 

 exudate and appear upon the surface as an adherent mass. 



The mesenteric lymph-glands through which the lymph passes from 

 the infected mucosa are tumefled and may be congested and hem- 

 orrhagic. In the subacute or chronic cases the central portion of the 

 lymph-glands may be necrotic. The peritoneum adjacent to the in- 

 volved intestine is invariably affected with a subacute or chronic in- 

 flammation. The peritoneal inflammation is manifested in the early 

 stages by an excessive ontpouring of serous fluids, but as the process 

 continues there is a tendency to organization and limited fibrous 

 proliferation which is prone to produce adhesions. 



When complicated with the filtrable virus disease, the lesions of in- 

 fectious necrotic enteritis and those that are attributed to hog chol- 

 era prevail. In the combination of the two diseases the lymph-gland 

 lesions are more prominent than in infectious necrotic enteritis. 



Infectious necrotic enteritis and swine plague sometimes occur 

 simultaneously in an animal, and the pulmonary lesions of swine 

 plague will then be noted in addition to the lesions of enteritis. 



Those cases of infectious necrotic enteritis complicated with para- 

 typhoid infections are sometimes difficult to differentiate from the le- 

 sions occurring in hog cholera and infectious enteritis. The involve- 

 ment of the peritoneum is probably more intense in paratyphoid in- 

 fections and the adhesions are more marked. 



Hympioms. — The symptoms of infectious necrotic enteritis are vari- 

 able, and the intensity of the symptoms manifested is not proportioned 

 to the intensity and extent of the lesions. Hogs .apparently in the best 

 of health may reveal lesions indicative of a chronic infectious enteri- 

 tis on autopsy while swine manifesting the usual symptoms of this 

 disease may show very limited lesions on autopsy. The infection acts 

 more rapidly and is more destructive in some cases and is slow going 



