Diagnosis. 277 



must always be considered. On the other hand, ii there is pres- 

 ent a pure hemorrhagic septicemia, or only an acute croupous 

 catarrhal, hemorrhagic, or a necrotic pneumonia, with or with- 

 out a fibrinous pleurisy, or if the case shows chronic remnants 

 of a pre-existing acute pneumonia (large necrotic areas, seques- 

 ters) then the anatomical changes, together with the micro- 

 scopical and cultural tindings, do not clear the true nature of 

 the affection. In such cases filtration tests are final, and if a 

 positive result is obtained with these the presence of a cholera 

 infection is thereby established. Still, a negative result of 

 such a test is not conclusive; as the cholera virus which has been 

 present in the body fluids may already have disappeared from 

 the body to a great extent or entirely. In such cases the diag- 

 nosis must depend upon whether the animal comes from a herd 

 infected wdth hog cholera, and wdiether in any of the other ani- 

 mals there were any lesions pointing to an infection of hog cliol- 

 era, or if a case represents a sporadic affection from a herd 

 which has proved healthy. It is essential therefore, in such 

 cases, to consider the epidemiologic factors, and to attach to 

 them their appropriate value, establishing the diagnosis. 



Of course this presents far greater difficulty in reaching 

 a diagnosis, when compared with the former conditions, in which 

 the bacteriological demonstration of bipolar ovoid bacteria or 

 cholera bacilli in the organs showing the inflammatory changes 

 were alone sufficient for the determination of the disease. By 

 such findings the disease was designated as hog cholera or 

 swine plague. At present however the demonstration of these 

 bacteria, whether in the blood or in the organs, is not of con- 

 clusive importance for the establishment of the diagnosis of 

 hog cholera or swine plague. It now becomes necessary to 

 consider the gross anatomical changes of the organs, in doubt- 

 ful cases also the epidemiologic accessory circumstances, and 

 the nature of the affection of other animals in the same herd. 



In bacteriological examinations the simple microscopic examination does not 

 always give positive results, but with the aid of culture and agglutination tests 

 it is in most instances possible to demonstrate the bacteria which participate in 

 causing the pathological processes. Animal inoculations with material from lesions 

 as a rule is only adopted for the demonstration of the septicemia bacillus, as 

 small animals are killed by these organisms in from 24 to 36 hours, and their blood 

 or the exudate of the abdominal cavity contains in such instances only this bacillus, 

 even though the inoculated material also contained the cholera bacillus. 



Swine erysipelas frequently greatly resembles a septi- 

 cemic form of hog cholera, especially when there are only few 

 and small hemorrhages present in the internal organs, such 

 cases usually occurring in the beginning of outbreaks. The 

 microscopical finding of erysipelas bacilli in the blood or in 

 the spleen of course establishes the diagnosis of erysipelas. It 

 is advisable however to postpone the final decision in negative 

 findings and to depend on the autopsies of other animals which 

 may die or which are slaughtered in emergency. If hog cholera 



