MORBID ANATOMY 23 1 



Switzerland, Denmark and England. A few cases have been 

 observed in this country. Sir John M'Fadyean has proposed 

 the name Johne's disease for this affection. 



ij 160. Etiology. The cause of this disease is supposed 

 to be an acid-fast bacterium which is found in large numbers 

 in the affected mucosa, and also in the mesenteric and colic 

 lymphatic glands. Morphologically this organism closely re- 

 sembles the tubercle bacterium. It varies in size from i to 2/< 

 in length and a few are said to attain to 4//. It stains uni- 

 formly but occasionally the longer forms show alternating 

 stained and unstained segments. It is remarkably acid-fast. 



According to M'Fadyean this organism is not iuoculable 

 to either guinea pig or rabbits. It has as yet not been culti- 

 vated on artificial media. 



This bacterium apparently does not form a strong cell 

 poison and hence the absence of necrosis. On the other hand 

 the tissues appear to be almost powerless to restrain its multi- 

 plication and invasion. 



The period of iyiciibation is not known. 



§ 161. Symptoms. The first symptom to be observed 

 is a loss of flesh, although the appetite remains normal. The 

 hair becomes roughened and the animal presents an unthrifty 

 appearance. Diarrhea soon sets in. As a rule, the diarrhea 

 is profuse and persistent from the time it begins, although it 

 may sometimes be checked temporarily b}' giving dry food 

 and by the administration of astringents. 



§ 162. Morbid anatomy. The lesions are primarily in 

 the small intestines, but, as a rule, involving the large intes- 

 tines, before death takes place. The distal part of the small 

 intestines is most involved. The lesion is in the mucous 

 membrane and even in seriously ill animals it is the only 

 lesion that has been found. In some cases the acid fast bac- 

 teria invade the submucosa in which ca.se the wall of the in- 

 testine becomes thickened. In proportion to this thickening 

 the mucosa shows more or less coarse wrinkling. Ulceration 

 is not observed, and there is very little congestion. 



