220 THE INFECTIOUS DISEASES. 



While some forms of glanders nodules somewhat resemble in gross 

 and microscopic appearance certain forms of miliary tubercles, the ab- 

 sence in the former of coagulation necrosis and of giant cells, and the 

 tendency to rapid disintegration and softening in the latter will usually 

 suffice for the distinction between the two sets of lesions. But the 

 demonstration of the bacilli characteristic of each is in all cases decisive. 



Characters of the Bacillus Mallei. 



The Bacillus mallei is a slender bacillus proportionately thicker than the tubercle 

 bacillus, with rounded ends, occurring singly or in pairs (Fig. 103). It stains easily 

 with the auilin dyes, but readily gives up the color in presence of even feeble decoloriz- 

 ing agents such as dilute alcohol or acids. It is left decolorized by 

 Gram's method. When stained, uncolored areas are apt to remain 

 in the body of the germ. Whether these are spores or not is not 

 yet definitely determined. 



In the tissues the bacilli may be stained with Loffler's alkaline 

 methylene blue. 



FIG. 1(8. BACILLUS The glanders bacillus grows readily on almost all of the ordi- 



MALLEI. nary artificial culture media, and best at blood heat. The growths 



on solid media are apt to be viscid. On potatoes it forms in two 



or three days an abundant yellowish pellicle which in a few days darkens and finally 



becomes brown in color. It gradually loses its virulence in successive generations of 



artificial cultures. The germ is easily killed by moist heat, but may remain alive in 



a dried state for months. Field mice and guinea-pigs are very susceptible to infection 



with the Bacillus mallei, and after inoculation develop highly characteristic local and 



general lesions. 



In cases in which an early diagnosis is imperative it is w T ell, in addition to the mor- 

 phological examination and cultures of the suspected exudate, to inject a small amount 

 into the peritoneal cavity of a male guinea-pig. If the virulent glanders bacilli be 

 present, within two or three days the testicles will swell and develop an intense sup- 

 purative inflammation. 



As the glanders bacillus grows in nutrient broth a proteid substance or substances 

 develops, which when concentrated by evaporation of the broth is called mallein. 

 This substance prepared a_nd administered to horses suffering from glanders, as tuber- 

 culin is prepared and administered to tuberculous cattle (see page 225), gives a similar 

 temperature reaction, and is thus an important diagnostic agent. 1 



Other Bacilli Belated to Bacillus Mallei. 



Several bacilli, apparently related to the B. mallei, have been found in various 

 lesions in men and lower animals. Thus an organism called Bacillus pseudotuberculosis 

 has been found in certain nodular lesions somewhat resembling tubercles which are 

 especially frequent in rodents. B. pseudotuberculosis liquefaciens has been described in 

 a series of cheesy nodules of the peritoneum, pancreas, and liver in man. In this group 

 also belong organisms which have been found in noma. 



Chancroid. 



In the lesion of " soft chancre " (chancroid) and the discharge from it a small oval 

 bacillus ("Ducrey's bacillus") has been frequently found either clustered or in chains. 

 It stains icadily with methylene blue, although it easily loses the color. It usually 

 occurs with other micro-organisms, and has been found, though not usually, in the 

 buboes, often occurring with the sore. It has been obtained in pure culture, in rabbit 



'For a resume of characters of the glanders bacillus see Wladimiroff 'in Kolle and 

 Wassermann's "Handbuch dcr Mikroorganismen," Bd. ii., p. 706. 



