FOOD POISONING. 57 



will be sterilized, and then selected molds and bacteria will be sown 

 in it. In this way the flavor and value of a cheese will be deter- 

 mined with scientific accuracy, and will not be left to accident. 



Canned Foods. — As has been stated, the increased consumption 

 of preserved foods is accountable for a great proportion of the 

 cases of food poisoning. The preparation of canned foods involves 

 the application of scientific principles, and since this work is done 

 by men wholly ignorant of science it is quite remarkable that 

 harmful effects do not manifest themselves more frequently than 

 they do. Every can of food which is not thoroughly sterilized 

 may become a source of danger to health and even to life. It 

 may be of interest for us to study briefly the methods ordinarily 

 resorted to in the preparation of canned foods. With most sub- 

 stances the food is cooked before being put into the can. This 

 is especially true of meats of various kinds. Thorough cooking 

 necessarily leads to the complete sterilization of the food; but after 

 this, it must be transferred to the can, and the can must be prop- 

 erly closed. With the handling necessary in canning the food, 

 germs are likely to be introduced. Moreover, it is possible that 

 the preliminary cooking is not thoroughly done and complete ster- 

 ilization is not reached. The empty can should be sterilized. If 

 one wishes to understand the modus operandi of canning foods, 

 let him take up a round can of any fruit, vegetable, or meat and 

 examine the bottom of the can, which is in reality the top during 

 the process of canning and until the label is put on. The food 

 is introduced through the circular opening in this end, now closed 

 by a piece which can be seen to be soldered on. After the food 

 has been introduced through this opening the can and contents 

 are heated either in a water bath or by means of steam. The open- 

 ing through which the food was introduced is now closed by a cir- 

 cular cap of suitable size, which is soldered in position. 



This cap has near its center a "' prick-hole " through which the 

 steam continues to escape. This " prick-hole " is then closed with 

 solder, and the closed can again heated in the water bath or with 

 steam. If the can " blows " (if the ends of the can become con- 

 vex) during this last heating the " prick-hole " is again punctured 

 and the heated air allowed to escape, after which the " prick-hole " 

 is again closed. Cans thus prepared should be allowed to stand 

 in a warm chamber for four or five days. If the contents have 

 not been thoroughly sterilized gases will be evolved during this 

 time, or the can will " blow " and the contents should be discarded. 

 Unscrupulous manufacturers take cans which have " blown," prick 

 them to allow the escape of the contained gases, and then resteril- 

 ize the cans with their contents, 'close them again, and put them 



VOL. LVI. — 5 



