BACILLUS MALLEI AND GLANDERS 789 



until it has assumed a deep reddish-brown hue. In using this feature 

 of the growth diagnostlcally, it must not be forgotten that a very 

 similar appearance upon potato occurs in the case of B. pyocyaneus. 



Biological Considerations. Bacillus mallei is aerobic. 3 Growth 

 under anaerobic conditions may take place, but it is slow and 

 impoverished. The most favorable temperature for its cultivation 

 is 37.5 C. It fails to develop at temperatures below 22 C. or above 

 43 C. On artificial media, if kept cool and in the dark, and in 

 sealed tubes, the glanders bacillus will retain its viability for months 

 and years. On gelatin and in bouillon, it lives for a longer time 

 than on the other media. Exposed to strong sunlight it is killed 

 within twenty-four hours. Heating to 60 C. kills it in two hours, 

 to 75 C. within one hour. Thorough drying kills the glanders 

 bacillus in a short time. In water, under the protected conditions 

 that are apt to prevail in watering-troughs, the bacillus may remain 

 alive for over seventy days. The resistance to chemical disinfectants 

 is not very high. 4 Carbolic acid, one per cent, kills it in thirty 

 minutes, bichlorid of mercury, 0.1 per cent, in fifteen minutes. 



Pathogenicity. Spontaneous infection with the glanders bacillus 

 occurs most frequently in horses. It occurs also in asses, in cats, 

 and, more rarely, in dogs. In man the disease is not infrequent 

 and is usually contracted by those in habitual contact with horses. 

 Experimental inoculation is successful in guinea-pigs and rabbits. 

 Cattle, hogs, rats, and birds are immune to experimental and spon- 

 taneous infections alike. 



Spontaneous infection takes place by entrance through the 

 broken skin, through the mucosa of the mouth or nasal passages. 

 Infection in horses not infrequently takes place through the digestive 

 tract. 5 In all cases, so far as we know, previous injury to either 

 the skin or to the mucosa is necessary for penetration of the bacilli 

 and the development of the disease. 



Glanders in horses may occur in an acute or chronic form, 

 depending upon the relative virulence of the infecting culture and 

 the susceptibility of the subject. The more acute form of the disease 

 is usually limited to the nasal mucosa and upper respiratory tract. 

 The more chronic type of the disease is often accompanied by mul- 



3 Loeffler, loc. cit. 



4 Finger, Ziegler's Beitr., vi, 1889. 



5 Nocard, Bull, de la soc. centr. de med. vet., 1894. 



