IMMUNITY AND SUSCEPT3ILITY 71I 



cells. It is claimed that this cytotoxin produces on injection symptoms 

 similar to those noted in eclampsia and it has been suggested that the 

 production of such a body in the pregnant woman from the placental 

 cells may be the cause of this serious condition. Liepmann claims to 

 have demonstrated placental constituents in the blood of pregnant 

 women by means of the precipitin test. • These bodies must be the 

 antigen of cytotoxins. He states that when the blood of the pregnant 

 woman is mixed with the specific syncytiolysin produced by im- 

 munizing an animal with human placenta that a precipitate occurs. 

 He suggestst he possibility of a serum test for pregnancy. Abderhalden 

 has reported some interesting results with the serum test for preg- 

 nancy and cancer. His findings cannot, however, be regarded as 

 conclusive. 



Cytotoxins are similar to bacteriolysins and hemolysins. They 

 consist of amboceptors which are activated by the complement which is 

 normally present in the serum or other body fliiids. 



' The Opsonins and Phagocytosis. — It was shown a number of 

 years ago that certain types of leucocytes and other body cells were 

 capable of ingesting bacteria and other plant and animal cells. The 

 mechanism of this process was not known until Wright and Douglas 

 demonstrated certain substances in the blood serum and other body 

 fluids which have the power of rendering the bacteria susceptible to 

 phagocytosis. These substances are known as opsonins (Gr. I pre- 

 pare food for). The phenomena of the phagocytosis depend almost 

 wholly on these special opsonins. Leucocytes which have been washed 

 free from all serum will not take up bacteria except a few in rare in- 

 stances. Bacteria which have been placed in contact with blood serum 

 or other body fluids may be thoroughly washed, and then when they 

 are placed in contact with the leucocytes, they will be taken up. The 

 opsonin reacts chemically with certain substances within the bacteria, 

 and so to speak, sensitizes them. Opsonins are present in many normal 

 serums for the various bacteria. They may be produced in animals 

 not containing them by the process of immunization with various 

 antigenous microorganisms. Opsonins are destroyed at about 60° 

 for thirty minutes, but there is some variation among them. When 

 kept at 0° opsonins will remain active for several ''days, but at a 

 temperature of the body, 37", after the serum has been withdrawn, 

 they rapidly deteriorate. Many opsonins have the structure of 



