PATHOGENIC BACTERIA. 325 



the southeastern part of Asia within a few years. In the 

 Middle Ages, and in succeeding centuries, it devastated many 

 of the countries of Europe, where it was one of the most im- 

 portant of the pestilences that went in those days by the name 

 of the "plague." It appears to have been the disease known 

 in English history as the "black death."* 



Paraplague Bacillus. Neumann! described an organism 

 which he isolated from rats in Hamburg which differs from B. 

 pestis bubonicas only in that it produces no results when in- 

 jected subcutaneously or intraperitoneally into rats and, further- 

 more, in that agglutination 'tests were negative. Breathing 

 into the lungs of very minute quantities was fatal for rats. 



Bacillus Aerogenes Capsulatus. A thick bacillus, 3 to 6 

 /* in length, frequently capsulated, discovered by Welch and 

 Nuttall. The capsules may be found in preparations from 

 animal tissues, but rarely in cultures. It sometimes forms 

 spores, chiefly in cultures on blood-serum. The vegetative 

 forms are destroyed at 58 C. moist heat in ten minutes, but the 

 spores withstand boiling nearly eight minutes. It is not mo- 

 tile. It stains by Gram's method. It. is anaerobic, and is 

 readily cultivated by Buchner's method for anaerobes. It 

 grows best at the body temperature, but will grow at the room 

 temperature. It may liquefy gelatin slowly or not at all. The 

 growths are whitish. In media containing lactose, dextrose or 

 saccharose it produces an abundance of gas; but according to 

 Welch, it is also able to form gas from proteids. Milk is co- 

 agulated, and the reaction becomes acid. Gas forms upon 

 potato, where the growth is thin and grayish-white. 



It occurs in the intestine of man and various other animals, 

 in soil, sewage and water. It is not usually pathogenic for 

 rabbits and mice. In guinea-pigs, sparrows and pigeons it may 



*For further details concerning plague consult articles by Parker, Novy 

 and Flexner. Transactions o}. the Association American Physicians. 1902. 

 Calvert. American Medicine. January 24, 1903. 



~\Zeitschr. }. Hygiene. XLV., No. 5. 1903. 



