1917] Studies on Coccobacillus Acridioruni D'Herelle 49 



B. Symptoms of the Disease. 



The time elapsing between infection and the manifestation 

 of the symptoms characteristic of the disease depends on the 

 virulence of the organism, and may vary from a few hours to 

 several days. Diseased locusts become sluggish and more or 

 less paralyzed, losing to some extent the power of leaping. The 

 excrement is black and fluid, and when the insect is dissected it 

 is found that the contents of the digestive tract are black and 

 more or less slimy. After death putrefaction proceeds rapidly 

 and the integument becomes blackened. 



Bacteriological or microscopical examination reveals the 

 presence of the coccobacillus in the intestinal tract, the blood 

 and faeces in practically pure culture. 



C. Increasing the Virulence of the Organism. 



It was the experience of d'Herelle and subsequent workers 

 that the coccobacillus when grown in artificial culture media 

 becomes very much weakened, but that the virulence could be 

 progressively increased by passing the organism through a 

 succession of locusts. 



In order then to obtain a culture sufficiently strong for our 

 experiments it was necessary thus to increase the virulence. 

 The first lot of locusts was inoculated with a suspension of the 

 original culture. On analyzing the contents of the intestines of 

 locusts killed by this injection we obtained a pure culture of the 

 coccobacillus. We decided then to use a suspension of the 

 intestinal contents of the dead locusts in our further injections. 

 Parallel with this we ran what we termed "a pure culture series," 

 that is, a series in which the intestinal contents of the dead 

 locusts were plated out on 1% beef peptone agar, incubated at 

 30° C. for eighteen hours, and then from the plates a typical 

 colony selected and this pure culture used for inoculating the 

 next lot. By the first method we obtained a virulent culture 

 much sooner than by the second. 



Our method of procedure was as follows: The dead locust 

 was placed for a few minutes in alcohol. Upon removal from 

 the alcohol its body was split along the back with a sterile pair 

 of scissors and a portion of the digestive canal severed. The 

 cut portion was removed with sterile forceps, dropped in a test 

 tube containing 10 cc. of sterilized water and triturated. The 

 suspension thus obtained was used in inocluating the healthy 

 locusts. 



