REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 113 



the border slightly thickened and very red. There was no adherent 

 slough. Some of the ulcers corresponded with the mouths of the 

 flask-shaped mucous glands. 



The exciting cause seems to attack the membrane from the sur- 

 face, for the submucous tissue is not infiltrated with cells to any 

 extent. In hog cholera very extensive infiltration quite invariably 

 accompanied the ulceration, so as to make the intestinal wail very 

 brittle. 



In another case the mucous membrane appeared as if gnawed or 

 eaten away in large patches. The diphtheritic deposit and subjacent 

 membrane in state of necrosis had very likely been shed as a slough, 

 leaving the ragged, depressed surface. 



The pathological process in the large intestine is distinctly ex- 

 udative, diphtheritic in swine plague; in hog cholera it is essentially 

 necrptic or ulcerative. In the latter the virus may act not only from 

 the intestine but also from the blood. In the former it perhaps 

 never acts from the blood, but only from the intestine. 



The lesions of the intestinal tract are always co-existent with the 

 specific broncho-pneumonia and without doubt secondary to it, be- 

 cause we frequently have encountered lung disease without intestinal 

 disease. The origin of the latter may be accounted for in two ways. 

 The virus enters the digestive and the respiratory tract at the same 

 time, or else it gains a foothold in the lungs first and thence reaches 

 the intestines. This is possible, for the bronchi are filled with bac- 

 teria imbedded in a large quantity of purulent mucus, which has 

 come from the diseased alveoli and bronchioles. They may be 

 coughed up into the mouth and swallowed and lodge at first in the 

 mucous glands of the large intestines, where they are well protected 

 while multiplying. The remainder of the mucous membrane may 

 then be attacked if the animal be weak or the virus especially active. 

 The simultaneous attack of lungs and large intestine is perhaps very 

 rare. Feeding pigs with large quantities of culture liquid and with 

 rabbits which have died after inoculation does not produce any lesions 

 whatever. We must therefore consider the lungs the most vulnerable 

 and the intestines only secondarily so. This view is supported by the 

 fact that in the early and most pronounced cases of the Washington 

 outbreak the intestinal lesions were very marked, but disappeared in 

 the progress of the disease. The virus, at first very powerful, became 

 slowly attenuated, being unable to attack the mucous membrane of the 

 intestines and therefore confined to the lung tissue. Intestinal lesions 

 are thus always associated with the severest lung disease, which in 

 turn is characterized by an abundant muco -purulent secretion in the 

 air passages. 



Diagnosis. The disease just described cannot fail to be recognized, 

 as it seems to be the only severe disease of the lungs among swine of 

 which we have any knowledge. That exposure may bring on croup- 

 ous pneumonia we do not deny ; but the character of the ordinary 

 croupous pneumonia among animals is such that it can be readily 

 distinguished from the irregular atypical infectious broncho-pneu- 

 monia which we have just outlined. li is barely possible, however, 

 that the disease may be confounded with other lesions which we have 

 met now and then in post mortem examinations. 



Collapse. The small ventral lobes which hang down on either side 



of the heart are very frequently collapsed (atelectasis). The affected 



lobe is small, of a bright red, soft to the touch, but without crepitation. 



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