CONTROL OF BACTERIAL DISEASES 249 



gastric juice of the stomach is strongly germicidal, these being 

 nature's provisions for turning the food over to the absorp- 

 tive organs germ-free. Breaks in the skin and mucous mem- 

 branes and the mouth are the great channels of entrance for 

 germs, and the fact that there are so many preventable in- 

 fections proves that under modern conditions of life nature's 

 provisions need constant reenforcement. In normal breathing 

 through the nostrils the germs are caught before they reach 

 the lungs, so that even pulmonary tuberculosis is coming 

 more and more to be considered a mouth infection, reaching 

 the lungs either by way of inflamed tonsils or by way of 

 stomach, intestine, thoracic duct, and circulation. 



When the role of bacteria in causing disease was first dis- 

 covered, chemical poisons .were sought which might kill the 

 germs without quite killing the patient. Carbolic acid (phe- 

 nol), mercuric chloride (corrosive sublimate), and formalin 

 were the germicides first used most extensively, and the gov- 

 ernment standard of efficiency, " the phenol coefficient," is 

 the germ-killing power of phenol. Later came the delicate, 

 specific, exact antitoxins and resistance serums that kill the 

 particular germ and have no poisonous action on the cells 

 of the body. Other nonpoisonous germicides, especially the 

 hypochlorites, from general use in purification of drinking 

 water and sewage, are being adapted to dairy, home, and 

 personal use. Here oxygen is the active germicide, and the 

 end products of the reaction are harmless calcium chloride 

 in case of hypochlorite of lime, and, with sodium hypo- 

 chlorite, sodium chloride, or common salt. 1 



1 "Three grains of a practically harmless substance will kill the myriads 

 of germs in a barrel of water. To do the same work with the poisonous cor- 

 rosive sublimate would require at least one ounce, or of the equally poison- 

 ous carbolic acid five pounds (p. 23). ... Hypochlorous acid is one of the 

 most powerful oxidizing agents known to chemists. The ' acid mixture ' 

 will, within a minute, kill spores which resist 5 per cent solution of carbolic 

 acid for weeks" (p. 54). Hooker, Chloride of Lime in Sanitation, 1013 



