MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 769 



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-pnuemonia 

 appear and more or less pleurisy. 



Bact. mallei shows no flagella and is non-motile. It is a small bacterium o. 2 s/j to 

 0.4M thick by 1.5/1 to 3ju long with rounded ends (Fig. 161). Spores have not been 

 demonstrated. It is generally single. Coccus forms sometimes appear and even 

 short threads when grown on certain media; e.g., potato. It decolorizes by Gram's 

 method and is not easily stained by the aniline dyes. This bacterium grows fairly 

 well between 25° and 42° on potato, glycerin agar, or blood serum. The guinea 

 ~ pig gives a reliable diagnosis by inoculation, showing a diagnostic reaction within 

 four or five days. Diagnosis may also be confirmed by the agglutination test in 

 dilution of about i : 1000 or more and by the complement fixation test. Satis- 

 factorily stained in tissue section by Kuehn's carbol-methylene blue. Its growth is 

 limited at an upper range of about 42° and the culture is killed at SS° in about five 

 minutes. Bact. mallei is difficult to isolate by culture methods being a slow grower 

 and easily lost beside faster growing organisms. It can be better isolated by guinea- 

 pig inoculation. In MEBw .th it is both aerobic and anaerobic 



Fig. i6r. — Bacterium woMeJ. Froitt pure culture on glycerin agar. X 1000. 



' (From Migula.) 



The virus escapes from the body in various ways. Elimination 

 is most common in morbid discharges from the nose, pharynx, trachea, 

 and in pus from farcy buds and abscesses. 



Bact. mallei may be spread directly from the diseased animal to the 

 susceptible animal, or the dissemination may be by way of intermedi- 

 ate objects; e.g., troughs, feed boxes, water pails, etc., and perhaps 

 also by inhalation. 



49 



