Immunity 201 



laboratory, where no immunity is brought into play, capsules do not 

 form on the groups mentioned. 



The encapsulated forms are not subject to phagocytic action, and 

 some even continue to produce more and more powerful poisons to 

 injure the unlucky phagocyte which may devour it. 



It is assumed that inflammations and fevers probably cause an 

 increased production of phagocytes and chemical neutralizations to 

 protect the body in injury and disease. 



The amboceptors anchor soluble poisons only when the complement 

 is present. 



Similarly, phagocytes will not engulf bacteria unless the bacteria 

 have first been prepared for such engulfing by substances in the normal 

 blood serum similar to the complement called opsonins. If an animal 

 has been immunized already by repeated introductions of bacteria, still 

 more resistant bodies called bacteriotropins appear. These bacterio- 

 tropins (which are only a sort of outstanding opsonin in immune sera) 

 act as opsonins and prepare the bacteria for the phagocytes. Opsonins, 

 bacteriotropins, and in fact all substances which prepare foreign sub- 

 stances for the phagocytes, are called cytotropins. 



When foreign bodies of any kind dissolve body substances, they are 

 said to be cytolytic (kytos-cell+lysis-dissolving) if they dissolve the 

 cytoplasm ; haemolytic, if they dissolve the red substance (haema=: 

 blood) in the blood cell ; hepatolytic (hepar=liver) if they dissolve liver 

 cells, etc., etc. Such lysins are usually antibodies. 



If a reaction can be produced, which will cause bacteria or cells to 

 clump together, such clumping is called agglutination, while the sub- 

 stances in immune sera which cause agglutination are called agglutinins. 

 This is commonly called the Widal reaction. Agglutination is so specific 

 that the serum of an individual suffering from typhoid fever, or even 

 the serum of one who has had the disease, will cause the clumping 

 of typhoid bacilli when a few drops of it are placed in a culture of the 

 bacilli. 



If any foreign protein substance is injected into any of the higher 

 animals, new substances similar to antibodies are formed. These are also 

 specific in acting on the same protein substances by causing a cloudy 

 precipitate, and sometimes by changing the protein by breaking it up 

 into simpler substances, some of which are poisonous. This fact makes 

 it possible to tell whether blood stains are those of a human being or not. 

 For example, the clear serum of a rabbit can be treated with human 

 blood serum and, if even a portion of the dissolved human blood stain is. 

 then added, a cloudy precipitate forms, although this precipitate will 

 not form when blood from a lower animal is added. Similarly, if the 

 rabbit's blood be first treated with the blood of a lower animal, human 

 blood will not cause the precipitate. 



A strange phenomenon has also come forth in recent years, known 

 as an anaphylactic shock. This is probably connected in some way with 



