112 INFECTION. 



out the course of the disease. Gruber named this substance 

 agglutinin. It may be formed by the action of the bacteria 

 on the tissues ; or by the resistance of the tissues to the 

 infection. The second supposition is hardly tenable. The 

 agglutinating action may also be obtained by the addition of 

 chemicals to the blood. Neither the composition nor the 

 origin of this substance has as yet been determined definitely. 

 It is quite resistant to heat and chemicals. Emmerich and 

 Loew believe that agglutination is the first stage of the bac- 

 teriolytic action of the enzymes produced by bacteria. 



Precipitins : When typhoid cultures are mixed with the 

 blood-serum of typhoids, a precipitate (non-bacterial) is formed 

 which soon settles, leaving a clear supernatant fluid. The 

 same reaction is obtained with other bacteria and their cor- 

 responding blood-sera. The precipitate is called the pre- 

 cipitum, and the substance in the blood which induces the 

 precipitation is called precipitin. The " anti-sera " also belong 

 to this class. The precipitins are very resistant to heat and 

 chemicals. Nothing is known of their chemical composition. 



Lysins: Normal blood-serum is bacteriolytic to a slight 

 extent, but during the infection specific bacteriolysins are 

 formed, which are bacteriolytic for the specific germ and also 

 its congeners. The composition and nature of these bodies 

 are likewise still a matter of dispute, but it is strongly sus- 

 pected that the lysins are the same as the agglutinins, although 

 by no means identical. 



All these various substances are known as " anti-bodies," 

 and are the results of the action of foreign proteid matter on 

 certain living cells ; such results are chemical substances 

 which have a specific relation to the substance under the 

 influence of which they are produced. 



Pfeiffer's phenomenon: Pfeiifer discovered that if cholera 

 bacteria are placed in the peritoneal cavity of a guinea-pig 

 that has been immunized to cholera, the bacteria are dis- 

 solved by the peritoneal fluid. The bacilli become immotile, 

 swell, and break into small granules which disappear com- 

 pletely. The reaction is specific not only for cholera, but 

 also for typhoid and other organisms. This reaction is bac- 

 teriolytic, and is due to the lysins. 



