TEXT-BOOK OF BACTERIOLOGY. 253 



occupies no such prominent place in human pathology as do the 

 three others. We refer to glanders or malleus. 



This disease, which was known and feared in ancient times as 

 particularly fatal to horses and asses, sometimes infects human 

 beings, and generally ends in death. In the bacteriological study 

 of this affection, therefore, and especially in handling the micro- 

 organisms of which we are about to speak, caution is of the first 

 importance. Almost half a dozen cases could be cited in which the 

 neglect of necessary care has led to the death of the investigator. 



Although there were plenty of opportunities to study the dis- 

 ease and watch its progress, its nature and its causes long re- 

 mained mysterious, and even down to the middle of this century 

 doubts were entertained as to whether it was an infectious disease 

 or not. Then, indeed, the conviction gained ground that glanders 

 spreads only by infection from animal to animal, and people began 

 to seek after the causes of the infection. 



In the year 1882, soon after the discovery of the tubercle bacillus, 

 Loffler and Schiitz recognized as the bearer of the infecting virus a 

 definite species of bacterium, the glanders bacillus, which they found 

 within the infected tissues. This was cultivated outside the animal 

 organism, and at last transmitted successfully from the artificial cul- 

 tures, so that its specific importance no longer admitted of a doubt. 



The glanders bacilli are small, slender rod-cells with rounded 

 ends, somewhat shorter and decidedly thicker than the tubercle 

 bacilli. They usually occur singly or in pairs, never in long threads. 

 They possess no motile power, though the extremely brisk mole- 

 cular motion which they frequently display in the hanging drop 

 gives them the deceptive appearance of spontaneous movement. 



The occurrence of spores has been positively proved by the ex- 

 periments of Baumgarten and Rosenthal, who succeeded in making 

 them visible by means of double staining. The genuine, sharply- 

 defined spores are not to be confounded with the frequently-occur- 

 ring light spots and gaps in the stained rod-cells, which by their 

 irregular shape and arrangement are clearry seen to be something 

 else. Loffler regards them as indications of involution and indicat- 

 ing an incipient decay. It is remarkable that the bacilli without 

 the help of spores retain their vitality almost three months in a dry 

 state. 



The glanders bacilli, like the majority of pathogenic bacteria^ 

 belong to the semi-anaerobic species. They require for their develop- 

 ment a tolerably high temperature, and are, therefore, at least by 

 preference, parasitic. They do not thrive under 25 C. nor over 42 

 C. Their optimum temperature is between 30 C. and 40 C. 



