Microorganisms in Relation to Man 583 



gar, and sugar ; and many spices, as pepper, cinnamon, cloves, 

 allspice, sage, and nutmeg. 



Preservative compounds are sometimes used which contain 

 certain mildly poisonous substances and are therefore germicidal. 

 In these compounds may be found such substances as formalin, 

 borax, boric acid, benzoic acid or benzoate of soda, saltpeter, 

 and salicylic acid. These, even in small quantities, may be 

 injurious to human health if their use is long continued. Be- 

 cause of the danger from cumulative poisoning, the use of such 

 preservatives is inadvisable. Their use in foods for the public 

 market is prohibited by law except in one or two cases, in which 

 the amount and kind of substance used must be kept within 

 certain limits and published on the labels. It has been a 

 common practice to preserve butter from becoming rancid by 

 the addition of a small amount of borax or formalin. One 

 twelfth of an ounce of pure borax in one quart of milk prevents 

 the growth of bacteria, and a very small amount of formalin 

 has a similar effect. But either practice is objectionable. 

 Formalin in milk and other foods has a chemical effect upon the 

 protein substances, rendering them difficult of digestion. 



Most food substances are safely and satisfactorily preserved 

 by thorough drying or cooking, by sugar, salt or vinegar solu- 

 tions, or by refrigeration. With clean handling and sterilized 

 containers these methods have all the advantages and none of 

 the dangers involved in the use of chemical preservatives. 



Only a few of the substances valuable as germicides or as 

 aseptics need be mentioned. Carbolic acid or phenol in dilute 

 solution is often used, but it is effective for only a few kinds of 

 bacteria and acts slowly except when very^strong. Chlorine in 

 the form of chlorid of lime is a valuable germicide and dis- 

 infectant for many purposes, such as waste water pipes and 

 sinks, but its general use is objectionable because of its pungent 

 odor. Formalin is becoming the leader of all disinfectants and 

 germicides, because of its convenience and effectiveness (page 

 598). Perhaps one of the best and most useful aseptics is 



