108 THE PATHOGENIC BACTERIA. 



tive phase immediately after the injection, in which the op- 

 sonic index is markedly lowered. This is usually followed 

 in a day by a positive stage of varying intensity and length, 

 usually lasting several days. He recommends that no second 

 injection be given until this second stage shows evidence of 

 declining. 



Aggressins. While investigating antibodies, Bail, in 1905, 

 enunciated the theory that the susceptibility to infection was 

 due, in some instances, to substances excreted by the bacteria 

 themselves, capable of overpowering the opsonins, etc., of the 

 infected host. He named these substances aggressins. His 

 theory has found many ready advocates and many ready foes. 



QUESTIONS. 



What are alexins ? 



What are antitoxins ? 



What are agglutinins ? 



What are precipitins ? 



What substances are called htemolysins ? 



Give an agglutination demonstration. 



Give a precipitin demonstration. 



How can lysins be demonstrated (in vitro)? (in vivo) ? 



What is necessary for the demonstration of haemolysis? What is meant 

 by H. complement in a serum ? What is antigen ? What is amboceptor ? 

 What is the Wassermann reaction ? What is the Noguchi modification ? 

 When is this test applicable ? What are opsonins ? Give Wright's technique 

 for determining the opsonic index in any person. What does Wright advo- 

 cate as a result of a positive opsonic test ? What are aggressins ? 



CHAPTER IX. 

 THE PATHOGENIC BACTERIA. 



THE PYOGENIC MICROCOCCI AND ALLIED BACILLI. 



THE most commonly found bacteria in pus are cocci (pyo- 

 cocci). A few are bacilli. The list includes : 



1. The Staphylococcus pyogenes aureus, albus, and citreus ; 

 the Staphylococcus cereus albus, the Staphylococcus cereus 

 aureus (Passet) ; the Staphylococcus cereus flavus (Passet). 



