MICROBIAL FOOD POISONING 589 



history suggesting food poisoning presents great difficulties and there 

 is good reason to believe that many instances of botulism fail to be 

 recognized during life or at autopsy. 



Various animals are subject to botulism. It has been established 

 that horses, mules and domestic fowl suffer and die from the disease 

 naturally. Dogs, cats, guinea-pigs and rabbits are susceptible to the 

 experimental disease. Cattle and chickens, though susceptible, seem 

 distinctly more resistant than horses. Graham and his associates have 

 brought forward convincing evidence to prove that at least some ex- 

 amples of "Forage poisoning" and " Ensilage poisoning" in domestic 

 animals are actually due to toxin of B. botulinus produced in the feed. 

 In these animals paralysis and muscular weakness are the prominent 

 manifestations. The disease has been designated as limber neck in 

 chickens and as cerebro-spinal meningitis, staggers or blind staggers in 

 horses. The proof that the disease is botulism rests upon the isola- 

 tion of B. botulimts from the food which gave rise to the poisoning, 

 or the effective protection of experimental animals against the poison 

 in the food by administration of specific botulinus antitoxin to them 

 while unprotected control animals are fatally poisoned, or by the 

 successful results of both these experimental procedures. 



Bacillus botulinus is a large rod 0.9 to 1.2^ wide and 4 to 6fj. long, 

 single, in pairs or in longer threads when growth conditions are unfav- 

 orable. The spore is oval and causes enlargement of the cell. It is 

 usually terminal or near one end, but may be central. The bacillus 

 is slightly motile, possesses 4 to 8 flagella and is Gram-positive. It is 

 a strict anaerobe, although, like other anaerobes, capable of active 

 growth in symbiosis with aerobic bacteria in the presence of air. Glu- 

 cose and salt in dilute solution favor growth but a concentration of 

 6 per cent, sodium chloride inhibits development. The optimum tem- 

 perature for growth is about 28C. Below 16 and above 37C. growth 

 is slight. The spores, according to Van Ermengem, are killed in a 

 half hour at 8oC. and by boiling for five minutes. More recent care- 

 ful tests by Burke have shown that this earlier work cannot be relied 

 upon and that there is considerable variability in the resistance of the 

 spores produced on different culture media. She found that some of the 

 spores resist boiling water for two hours and the spores of one strain 

 resisted heat in the autoclave at 5 pounds pressure for ten minutes. 

 The importance of these observations in relation to canned food is 

 obvious. 



