26 INFECTIOUS AND PARASITIC DISEASES. 



given them their reputation as curative principles. 

 The production of antibodies represents the reactionary 

 or fighting powers of the body above referred to, and 

 is its natural weapon of defense against disease. 



As the result of bacterial infections, distinctly differ- 

 ent antibodies are formed which owe their origin to 

 peculiarities in attack of the infecting agents. All 

 bacteria produce disease through their toxins, but 

 because the manner in which the latter are eliminated 

 is not the same for all, there arise differences both in the 

 nature of the protective substances, and the manner in 

 which these substances protect. From the standpoint 

 of disease-production bacteria may be divided in a 

 broad way into two classes, viz., (i) those that attack 

 the body rather through a diffusible poison, which they 

 excrete, than by enormous reproduction; and (2) those 

 in which multiplication is the primary or essential 

 phenomenon, toxin-excretion subsidiary. Bacteria of 

 the first order, through their toxins, give rise to sub- 

 stances which neutralize the latter, that is, antitoxins. 

 Bacteria of the second order, contrariwise, stimulate the 

 body to the formation of substances antagonistic to 

 the bacteria themselves, i.e., antibacterial or bacteri- 

 cidal substances. The protection that antibodies which 

 are bactericidal furnish the body comes through their 

 power of dissolving the bacteria which cause the 

 disease. If immunity against infection is, therefore, 

 contrasted from the standpoint of the etiological agents, 



