102 INFECTION AND IMMUNITY. 



atom groups in each of these substances possessed an affinity 

 for each other. These atom groups are represented on one 

 side in the cell protoplasm and on the other in the food, toxin 

 or other substance introduced into the blood. As the number 

 of these substances were varied, Ehrlich suggested the theory 

 that each cellular molecule was made up of a central atom 

 group and numerous side atom groups or chains, which he 

 called receptors. Under the influence of the stimulation of 

 any toxin the special receptors are overproduced, and it is 

 their increased presence in blood which produces immunity. 

 A passing remark, however, may only be offered on this 

 subject, and those who are interested must be directed to con- 

 sult larger works, in which these views are explained at 

 length. 



QUESTIONS. 



What is infection ? 



How are bacteria called which produce disease in animals? 



How is the action of pathogenic bacteria on the animal body explained ? 



When is a disease said to be septicsemic? When is it toxsemic? 



Name the three modes by which the animal body may be infected. 



What conditions favor infection ? 



What conditions in the infecting material increase its power? 



What conditions in the animal increase the rapidity of infection ? 



What part does the quantity of bacteria introduced in the inoculation play 

 in the infection? 



What is meant by attenuation ? 



What conditions of the cultures make the bacteria more virulent? 



What is the effect of passing for a number of generations pathogenic bac- 

 teria through artificial media ? 



What part does the mode of introduction of the bacteria in the animal body 

 play in infection? 



What is meant by double infection ? 



What is immunity? 



What is meant by natural immunity ? 



What is meant by acquired immunity ? 



Give some examples of natural immunity? 



What produces acquired immunity in animals? 



What are active and passive immunity? 



What artificial methods are used to produce immunity? 



What is meant by inoculation ? Vaccination ? Intoxication ? 



How does tissue suspension produce immunity? 



What influence does the injection of inert particles have upon immunity? 



What is meant by forced immunity ? 



What is meant by an antitoxic serum ? By an antimicrobic serum ? 



What classes of disease are protected against by antitoxic serum ? What 

 by antimicrobic serum ? 



How is this anti-action explained? 



