IMMUNITY 69 



1. Bacteriolysins. The first antibodies cause a 

 dissolving of the bacterial cells. These antibodies 

 are called bacteriolysins (adj., bacteriolytic) . There 

 is in all blood, whether normal or subjected to im- 

 munizing procedures, a substance called complement 

 which makes possible these combinations of antibody 

 and germ. 



2. Agglutinins. Agglutinins are substances which 

 cause clumping of bacterial cells, but do not dissolve 

 them. They are made use of in the diagnosis of some 

 acute fevers, notably in the Widal reaction of typhoid 

 (see Typhoid Fever). 



3. Opsonins. These are substances which act upon 

 bacteria and prepare them for consumption by the 

 white cells of the blood (leukocytes). These cells are 

 also migrating cells, as they leave the blood stream 

 and wander over the body. These leukocytes are also 

 called phagocytes (adj., phagocytic) because they can 

 consume foreign bodies. Bacteria are such, and it is 

 the task of these phagocytes to remove them. It 

 has been found that in some conditions their power of 

 consuming bacteria is below par, and, further, that if 

 small numbers of germs incapable of producing disease 

 are introduced, the power of these cells may be 

 increased. The bodies producing this increased eating 

 or phagocytosis are the antibodies, opsonins, sup- 

 posed not to act upon the white cells, but upon the 

 bacteria and make them more suitable as food for 

 the leukocytes. These phenomena have put a valuable 

 method of treatment in the physician's hand. In 

 subacute localized disorders, particularly, but also 

 in definitely acute and chronic troubles, injections 



