HARMFUL PRESERVATIVES 345 



solutions. Fish, especially cod and herring, are dried and salted. 

 The keeping of butter is due to the salt mixed with it. Vinegar 

 is another preservative. It, like salt, changes the flavor of mate- 

 rials kept in it and so cannot come into wide use. Spices are also 

 used as preservatives. 



Harmful Preservatives. — Certain chemicals and drugs, used as 

 preservatives, seem to be on the border line of harmfulness. Such 

 are benzoic acid, borax, and boracic acid. These chemicals may be 

 harmless in small quantities, but. unfortunately in canned goods 

 we do not always know the amount used ; also, as a rule, food that 

 needs such a preservative is of bad quality in the first place. The 

 Pure Food Law makes it illegal to use any of these preservatives 

 in food (excepting very small amounts of benzoic acid). Food 

 which contains this preservative must be so labeled and should 

 not be given to children or people with weak digestion. Unfor- 

 tunately, people do not always read the labels, and thus the Pure 

 Food Law is ineffective in its working. 



Summary. — The organisms that we call fungi, yeasts, molds, 

 and bacteria belong in two great groups, according to their life 

 habits. The parasitic forms such as the chestnut blight, the rusts 

 and smuts, and many bacteria are parasites and do much harm. 

 But a great number of bacteria and fungi, as saprophytes, live on 

 dead organic matter and are of incalculable value. Think of a 

 world in which no decay takes place, or in which there can be no 

 increase in crops. Life would be impossible without the bacteria 

 of decay and the nitrifying bacteria, which release simple com- 

 pounds of nitrogen for use. Bacteria which harm our foods are 

 kept under control by the use of preservatives, sterilization, re- 

 frigeration, and canning. 



Problem Questions 



1. Compare the habits of life in saprophytes and in parasites. 



2. Look up outside sources and see how many harmful fungi you can dis- 

 cover ; how many useful forms. 



3. How do yeasts and molds obtain food ? How do they digest food? 



4. Sum up the ways in which molds do harm and do good. 



5. Sum up the ways in which yeasts do harm and do good. 



6. Discuss the process of fermentation. 



7. Look up Trench Foot, a disease of the World War. 



