THE COLON, TYPHOID AND DYSENTERY BACILLI 337 



the serum of these animals has been found to be antitoxic as well as 

 bactericidal. Its use in treatment has given promising results and_ 

 seems to cause a reduction in the death rate of about 50 per cent. 



Paradysentery Bacilli. Flexner in 1899 isolated a bacillus 

 from cases of dysentery in the Philippines which at the time was 

 considered to be the same as the Shiga bacillus. Kruse, although 

 he found the Shiga bacillus in epidemic dysentery, found a some- 

 what different organism in " asylum dysentery" or pseudo- 

 dysentery, which proved to be identical with the Flexner bacillus. 

 Between 1901 and 1903 a number of strains of bacilli resembling 

 somewhat B. dysenteries were isolated -by different investigators 

 from epidemics of diarrheal disorder, especially in the Eastern 

 United States. The paradysentery bacilli are indistinguishable 

 from B. dysenteries in morphology or in cultures on ordinary 

 media. They are all much less toxic to rabbits than the Shiga 

 bacillus, and they all ferment mannite with the production of 

 acid, while the Shiga bacillus does not. 



The bacteria considered in this chapter are all inhabitants 

 of the alimentary canal (mouth, pharynx, intestine) of man or 

 other mammals. They are small bacilli, Gram-negative, without 

 spores and without the ability to liquefy gelatin. They vary 

 from each other in motility, possession of flagella, possession of 

 capsules, and in their ability to form poisonous substances and 

 to ferment various carbohydrates. Media containing various 

 carbohydrates along with an indicator such as litmus to show 

 the production of acid, and contained in fermentation tubes so 

 as to measure the production of gas, are very useful in differentiat- 

 ing 1 the various types of bacteria in this group. Thus, in a 



1 Hiss has devised a very useful medium for this purpose which obviates the neces- 

 sity of using the fermentation tube to detect the gas. His serum- water medium is 

 made by mixing beef serum, i part, with distilled water, 2 to 3 parts, and steaming 

 15 minutes to destroy enzymes. Pure litmus solution (about i part of a 5 per cent 

 solution to 100 parts of the medium) is then added to produce a deep blue color. 

 The medium is divided into several portions and i per cent of the desired carbo- 

 hydrate is added to its respective portion. The sugar serum-water media are then 

 sterilized at 100 C., on three days. Fermentation is shown not only by the redden- 

 ing of the litmus but also by coagulation of the liquid medium, and gas production 

 is shown by bubbles caught in the coagulum. (Hiss and Zinsser: Text-book of 

 Bacteriology, 1910, p. 132.) 



