714 MICROBIOLOGY OF DISEASES OF MAN AND DO:iSIESTIC ANIMALS 



them susceptible to phagocytosis by the polymorphonuclear leucocytes 

 and the epithelial and other body cells. They are designated as hemo- 

 opsonins. Occasionally iso- and autohemoopsonins are present in 

 normal sera. For example, in human blood serum, it is probable that 

 the process of red blood corpuscle destruction which takes place in the 

 spleen may be referred to the action of these tj^es of opsonins and 

 various phagocytic cells. 



Agglutinins. — Agglutinins are substances, present in the blood 

 serums and body fluids of normal and immune animals^ which 

 have the power of producing a clumping and sedimentation of the 

 microSrganisms causing the specific infection or used in artificial im- 

 munization. The relationship of the agglutinins to the phenomena of 

 immunity and the other antibodies which are produced during the 

 process of infection and experimental inoculation is not known. One 

 of the first agglutinins to be observed was that occurring in the blood 

 serum in cases of tjrphoid fever and the agglutination reaction is now 

 made use of in the diagnosis of this disease {Widal test). Agglutinins 

 are specific substances and at high dilutions only cause a clumping of" 

 the microorganisms which give rise to their formation (antigens). 



Normal Agglutinins. — Agglutinating substances, as above stated; are 

 frequently found in normal serums. In this case no direct connection 

 between their formation and specific micro6rganisms can be established. 

 Normal human serum frequently contains agglutinins for B. typhosus, 

 B. coli, Bact. dy sentence, and occasionally M. pyogenes var. aureus 

 and Msp. comma in certain rare cases. Agglutinins for B. typhosus 

 which are present normally in the serum may give rise to confusion 

 when this test is' used for the diagnosis of t3T)hoid fever. It is, there- 

 fore, necessary to dilute the serum of a suspected case of typhoid fever 

 at least one to forty or one to fifty times in order to exclude the normal 

 agglutinins and the so-called coagglutinins. 



The Production of Agglutinins. — Agglutinins may be produced arti- 

 ficially by the injection of bacteria, dead or alive, into the veins, sub- 

 cutaneous tissues or peritoneal cavity. In rare cases they may be pro- 

 duced by feeding the bacteria, injecting them into the air. passages of 

 the lungs or by rubbing them into the skin. It is probable that the 

 highest concentration of agglutinins results from the injection of dead 

 bacteria. It is, however, necessary that these bacteria be not subjected 

 to a temperature above 62°. Many pathogenic and non-pathogenic 



