MICROBIAL DISEASES OF MAN AND ANIMALS. 617 



serious with a probability of fatal termination. Ulcers may develop in 

 the nose or mouth with more or less discharge. Pustules appear involving 

 the skin, and abscesses involve deeper structures in various portions of the 

 body. 



The distribution of Bact. mallei in the animal body is shown by the 

 most common appearance of its disease in the skin, subcutaneous tissue, 

 mucous membranes, lymphatic system, lungs, liver, spleen and kidneys. 



The etiological factor is a small bacillus with rounded ends known as 

 Bact. mallei, discovered by Loeffler and Schiitz in 1882, and well demon- 

 strated to be the specific cause of glanders. 



Entrance is usually effected by way of a mucous membrane, fre- 

 quently the intestinal; sometimes by inoculation. The period of incuba- 

 tion seems variable and uncertain under natural infection, but in artificial 

 inoculation with virulent cultures, is very brief. 



Bact. mallei produces toxins in artificial media and presumably also 

 in body tissues; e.g., the well-known preparation called mallein. This 

 toxin (mallein) produces a distinct reaction by inoculation into glandered 

 animals, but is practically non-toxic for healthy equines. So far as known 

 Bact. mallei attacks the animal tissues as do many other microorganisms, 

 the harm resulting chiefly from bacterial toxins which give the local tissue 

 reactions leading to the lesions characteristic of glanders. 



In its action on tissues Bact. mallei resembles Bact. tuberculosis; but 

 shows a more rapid development of lesions and more active inflammation. 



Lesions are of two types a well-defined nodule followed by ulceration 

 and diffuse areas of infiltration. 



The nodule as it appears in glanders consists largely of lymphoid cells. 

 Nodules die at the center, suppurate, and discharge. This occurs 

 especially in the external form of glanders, which affects more commonly 

 the legs and head. Occasionally defined enlargements appear in the 

 involved lung areas. Pulmonary lymph glands are frequently enlarged, 

 and hardened. The superficial skin lesions are in the form of nodules 

 previously mentioned, which usually suppurate and ultimately heal. In 

 the deeper subcutaneous tissues there is a tendency to abscess formation. 

 Small nodules or tubercles commonly appear in the lungs of affected 

 horses. These vary in size from millet seed to as large as garden peas. 

 Various degrees of broncho-pneumonia appear and more or less pleurisy. 



Bact. mallei shows no flagella and is non-motile. It is a small bacillus 0.25^ to 

 thick by 1.5^ to 3.^ long with rounded ends (Fig. 106). It is generally single. 



