83 



The body rights disease in many ways. It will be sufficient for hy- 

 gienic purposes to teach but three of these ways: (i) the method of anti- 

 toxiues ; (ii) the metliod of antiseptics and (iii) the method of phagocyto- 

 sis. 



There ar many diseases in wliich the symptoms are caused, not by the 

 bacteria themselves, but by the poisons the bacteria manufacture. Thus, 

 in tetanus, or lockjaw, the bacteria grow, perhaps unnoticed, at the bottom 

 of the Fourth-of-July wound on the hand or foot ; but the chemical poisons 

 they manufacture, carried by the blood to the brain and spinal cord, cause 

 the spasms and convulsions that characterize the disease. In diphtheria 

 the bacteria rarely enter the body, but grow in grayish-white masses on 

 the moist surfaces of tlie mouth and throat. The chemical poisons they 

 manufacture, absorbed by the tissues, cause the paralysis and heart failure 

 that characterize the disease. 



The body has the power of forming substances that neutralize these 

 poisons. To these neutralizing substances the name antitoxine has been 

 given. 



This fact is of hygienic importance for two reasons: First, because it 

 is sometimes possible to assist the body in its efforts to form antitoxines, 

 by introducing into it antitoxines artificially prepared; and, second, because 

 the body's power to form these substances is modified by mode of life. 



A horse that has been repeated^' injected with the poisons manufac- 

 tured by the germs of diphtheria, grown on artificial culture media, de- 

 velops enormous amounts of diphtheria antitoxine. A few drops of the 

 serum of this horse renders harmless large quantities of diphtheria poison. 

 Through the use of diphtheria antitoxine in practical medicine, the mortal- 

 ity from diphtheria has been reduced from the 24 per cent, to 40 per cent, 

 it was, twenty years ago, to the less than 1 per cent, it now is, in well- 

 treated cases. Overwork, insufficient clothing, improper food, alcoholic ex- 

 cesses, lack of sleep, and other factors, so lower the antitoxiue-forming 

 power of the body as to greatly increase the dangers from infection. 



The second way of hygienic significance in which the body fights dis- 

 ease, is by the formation of chemical substances that, although they have no 

 influence on the chemical poisons manufactured by bacteria, have an even 

 more important propei'ty, that of killing the bacteria themselves. 



The presence of antiseptic, or bacteria-killing substances in the blood 

 and tissue juices is easily shown. One has but to mix bacteria with serum 



