One widely distributed organism known as _Bacillus proteus_ has been several times held responsible for food poisoning outbreaks, but it is not yet certain how far this accusation is justified. _B. proteus_ is related to _B. coli_, but most varieties do not ferment lactose and are much more actively proteolytic than the latter organism, as shown by their ability to liquefy gelatin and casein. Like _B. coli_, they form indol and ferment dextrose with gas production. Varieties of _B. proteus_ are found widely distributed in decomposing organic matter of all sorts. The evidence upon which this bacillus is regarded as the cause of food poisoning is not altogether convincing. The outbreak described by Pfuhl[60] is typical. Eighty-one soldiers in a garrison at Hanover were suddenly attacked with acute gastro-enteritis four to twelve hours after eating sausage meat. The meat was found to contain _B. proteus_ in large numbers, although it was prepared with ordinary care and was entirely normal in appearance, taste, and smell. Rats and mice fed with the sausage became ill and _B. proteus_ was isolated from the blood and internal organs. But these animals sometimes die when fed with quite normal meat, and _B. proteus_ and other common intestinal bacteria are often isolated from the body after death. _B. proteus_, in fact, is found in many animal foods and in the apparently normal human intestine. Like _B. coli_, it frequently invades the internal organs after or shortly before death. Finding _B. proteus_ in food or in the internal organs does not therefore constitute definite proof of any causal relationship. The evidence attributing other outbreaks to infection with _B. proteus_ is similarly inconclusive. It is equally uncertain whether the production of a poison in food by this species can in any degree be held responsible for meat poisoning. _B. proteus_ is common enough in decomposing food material and under certain circumstances is known to generate substances that are toxic for man. It is possibly true that toxic substances are produced in the early stages of decomposition by this organism. In the opinion of Mandel[61] and others, if any injurious effect at all is to be attributed to _B. proteus_, it is in the nature of an intoxication and not an infection (see chapter viii). So far as the existing evidence goes, the question of the responsibility of this organism for food poisoning is still an open one. FOOTNOTES: [49] Sawyer, _Jour. Amer. Med. Assoc._, LXIII (1914), 1537. [50] _Eng. News_, LXX (1913), 322. [51] Morse, _Report of State Board of Health of Mass._, 1899, p. 761. [52] R. H. Creel, _Reprint from Public Health Reports, No. 72_, Washington, 1912. [53] _Health Bull. No. 76, Pennsylvania State Department of Health_, December, 1915. [54] _Amer. Jour. Public Health_, II (1912), 321. [55] _Institution Quarterly_, III (1912), 18.