Pathogenesis. 269 



and further with the aid of McFadyean's apparatus for breaking up bacteria, 

 but he failed in immunizing test animals with the substances obtained by any of the 

 three methods. The toxicity of killed bacilli (endotoxins) is shown by the experi- 

 ments of Uhleuhuth and his co-workers, who succeeded in producing a typical ana- 

 tomical picture of hog cholera by intravenous injections of cultures heated to 60°G. 

 According to Bang's investigations, the necrophorus bacillus is also a partic- 

 ipant in the production of the necrotic processes, and as a matter of fact it 

 is very frequently found in large clumps at the base of the ulcers as well as in 

 the nodules along the border between the necrotic and living tissue. 



The bacillus suisepticus exerts its pathogenic action in a similar 

 way in cases of pure swine plague (see p. 127). In the peracute cases 

 it is found quite frequently in the blood more often than the bacillus 

 suipestifer. The lesions of hemorrhagic septicemia wliicli are found 

 at the autopsy of such cases are evidently largely due to its action. 

 Often, however, the frequent pneumonia and pleurisy is directly asso- 

 ciated with the activity of this organism. 



The fact that the bacillus suipestifer and the bacillus suisep- 

 ticus are very frequently actively concerned in hog cholera 

 besides the liltrable virus, explains why clinical as w^ell as ana- 

 tomical findings should vary to such a great extent from case 

 to case. In the majority of the dead or emergency slaughtered 

 animals in infected herds examination discloses an ulcerative 

 inflammation of the intestines and caseation of the lymph glands, 

 also necrotic inflammation of the lungs, fibrinous deposits on the 

 serous membranes, as well as hemorrhages, while careful bac- 

 teriological examinations prove the presence of both species of 

 the bacteria mentioned. In the course of some outbreaks, as 

 well as after the artificial infection of herds (by introducing 

 affected animals into healthy herds, the placing of a healthy 

 herd on infected premises), septicemic affections usually pre- 

 dominate. The first animals dead from the disease, which 

 probably had the least resistance, show acute catarrh of the 

 mucous membranes exclusively, and more or less numerous 

 hemorrhages, somewhat later pleuro-pneumonia may also be 

 present, wdnle on the mucous membranes of the intestines small 

 follicular ulcerations or superficial desquamation of the mucous 

 membrane may be seen here and there. Later the characteristic 

 intestinal changes of cholera develop, in constantly greater ex- 

 tension and intensity; first a superficial desquamation of the 

 epithelium, then a follicular ulceration, or a diffuse, diphtheritic 

 inflammation of the mucous membrane. At the same time the 

 pleuro-pneumonia occurs with greater frequency, so much so 

 that toward the end of the outbreak it is present in the great 

 majority of cases. In the animals wdiich still remain debilitated 

 after the acute outbreak has passed off changes of a chronic 

 character are present either in the intestines or in the lungs. 



These successive anatomical findings may be explained by 

 the fact that the most susceptible and the least resistant animals 

 are killed by the specific cholera virus at the beginning of the 

 outbreak, whereas the more resistant ^vithstand the primary 

 infection for a time and are only exhausted by the organic affec- 

 tions which develop later. 



