41 6 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



fever; they may be poisonous on account of actual disease or through 

 serious contamination due to living in dirty water; or they may be poison- 

 ous because of decomposition which has taken place after removal from 

 the water. According to the symptoms produced, there appear to be at 

 least three distinct varieties of shell-fish poisoning, one a purely gastro- 

 intestinal disorder, the second an involvement of the nervous system with 

 itching skin eruption and convulsions, and a third type resembling very 

 closely alcoholic intoxication. The exact nature of the microbic agents 

 concerned in these different types of poisoning is unknown. It is pretty 

 well established, however, that the poisonous character of shell-fish is 

 due either to their living for some time in dirty water, or to their too long 

 preservation, especially at high temperature, after removal from the water. 



MILK, ICE-CREAM AND CHEESE sometimes give rise to poisoning, and 

 although these instances are small in number in comparison with the 

 enormous amount of milk and milk products consumed, yet in the aggre- 

 gate they are numerous. That many human infections may be trans- 

 mitted by milk has already been pointed out. In the summer, milk is 

 undoubtedly a great factor in the infant morbidity and mortality, and 

 this poisonous action is largely due to bacterial changes in the milk. 

 Extraordinary precautions are therefore essential in the production and 

 care of milk to be used as food for children, particularly during the warmer 

 season of the year. Severe poisoning of adults with milk, ice-cream, or 

 cheese, is relatively less frequent. Cases which have been studied have 

 been traced to the development of B. coli or B. paratyphosus in these foods. 

 There is some evidence that other bacteria, probably strict anaerobes, are 

 also sometimes concerned. Strict cleanliness, proper refrigeration, and 

 pasteurization of milk of uncertain character, may usually be relied upon 

 to prevent milk poisoning. Ice-cream should be made only from whole- 

 some materials and with due regard to cleanliness in making it. The 

 causes of serious cheese poisoning are not definitely known, but such 

 poisoning may be avoided, to a large extent at least, by using only stand- 

 ard varieties of cheese of the proper odor and flavor. 



VEGETABLE FOOD POISONING, in an acute form, has followed the use 

 of sprouting and partly decomposed potatoes, and also various canned 

 vegetables, particularly those of high protein content, such as beans. 

 The large majority and possibly all of these cases are due to decomposition 

 changes in the foods, B. botulinus and B. proteus appearing to be the mi- 

 crobes most frequently concerned. 



