BACILLUS DYSENTERIC 143 



The dysentery bacillus is a short, straight, non- 

 motile rod with rounded ends. It is quite like the 

 typhoid bacillus in shape and size, but unlike this 

 germ, does not move actively. It may at times show 

 degenerated forms. It is usually single, but may be 

 in pairs. It stains easily. It grows both aerobically 

 and anaerobically, but better under the former con- 

 ditions. Its growth upon laboratory media is also 

 like that of the typhoid bacillus. Best development 

 occurs at 37 C. or 98 F., and death results when 60 C. 

 or 142 F.^is held for ten minutes. 



It resists freezing for a long time, possibly some 

 weeks. It is killed by drying only after long periods. 

 Its resistance to chemicals is practically the same 

 as that of typhoid bacilli. Animals do not contract 

 dysentery w r hen they take the bacilli by mouth, but 

 when germs or their toxins are introduced under the 

 skin, into the vein or peritoneum, profound intoxica- 

 tion occurs, with fall of temperature, peritonitis, diar- 

 rhea, and in some cases hemorrhage in organs or body 

 cavities. 



Dysentery Antiserum. Nevertheless, animals, notably 

 rabbits and horses, have been made to withstand 

 large doses by preparation with graded amounts. 

 They develop sera containing antisubstances to both 

 the endo- and extracellular dysentery toxins. This 

 serum has been used therapeutically in the treatment 

 of dysentery of the tropical variety, but it has not 

 been found useful in other cases; it is made only against 

 what is called the Shiga type of dysentery bacillus. 

 Thus passive immunity can be secured, but so far no 

 great success has met attempts to raise the resistance 



