88 DYSENTERY 



claiming that he had found the specific cause, and subsequent studies 

 by others have confirmed this claim. This organism is now generally 

 known as the Shiga bacillus. 



Two years later (1900) Flexner, in a report of an expedition to 

 investigate the diseases prevalent in the Philippines, described a bacil- 

 lus found in epidemics on these islands. It also was present in all cases 

 and agglutinated with dilutions of the blood serum of the sick. There 

 was for a time much discussion about the identity of these two organ- 

 isms. It would be profitless to follow these discussions since it is now 

 generally admitted that the differences are sufficient to justify the con- 

 clusion that they are different species, and this is now known as the 

 "Flexner" bacillus. There are two other bacilli capable of causing 

 dysentery. These are varieties of the Flexner organism. One is 

 known as the "His-Russell," and the other as the "Strong" bacillus. 



The Shiga Bacillus. This is a small plump rod with rounded ends. 

 It was at first believed to be motile, but closer study shows that it 

 has no flagellae and no active motion, although it demonstrates the 

 Brownian movements in a marked degree. It is sporeless and ordi- 

 narily it needs frequent transplantation in order to keep it alive. How- 

 ever, according to Martini, if an agar-culture tube be hermetically 

 sealed the rods disintegrate into a granular debris which is not easily 

 stained and shows no rods. If this granular mass, even after a year, 

 be placed in fresh medium, normal rods develop. This observation 

 has been confirmed by similar findings with the plague bacillus and it 

 should be more closely and thoroughly studied. Fresh cultures have 

 a sperm-like odor, while older ones develop trimethyl and ammonia. 

 Very old growths have a strong and penetrating fecal smell. It takes 

 the ordinary stains easily, but the staining is not always uniform ; some- 

 times it is polar. It develops on ordinary media without any char- 

 acteristic exhibitions. Culturally it is distinguished from the Flexner 

 and related dysentery bacilli by the fact that it develops no acid when 

 grown on media containing mannite, maltose or saccharose. The 

 Shiga bacillus is furthermore distinguished from the other organisms 

 by the development of a soluble toxin. This will be discussed in more 

 detail later. 



The Shiga bacillus is not highly resistant to unfavorable condi- 

 tions. It is easily destroyed by the usually employed disinfectants, 



