376 



DEFENCE 



COMPLEMENT 



AMBOCEPTOR 



to which he has given the names amboceptor and comple- 

 ment. The amboceptor (immune or intermediate body) 

 is a specific substance not destroyed by heat. The comple- 

 ment (or alexin) is a specific substance destroyed by heat. 

 It is present in nearly all sera. It is the complement which 

 has the hsemolytic action. The amboceptor has two afiuii- 

 ties, one for the red blood corpuscle, the other for the 

 complement. The complement combines with the proto- 

 plasm only through the ambo- 

 ceptor. This is shown graphically 

 in Fig. 73. It will be seen that 

 in a sense complement corre- 

 sponds to the toxophore and 

 amboceptor to the haptophore 

 group. 



When an emulsion of dead 

 bacteria is introduced into the 

 body antibodies are formed which 

 protect against any Hving bacteria 

 of the same kind which may 

 gain entrance later. This is the 

 basis of vaccine treatment. But 

 the immunity thus conferred is 

 not always entirely due to the 

 formation of antibodies. Another 

 class of substances is developed. 

 These are the Opsonins, the 

 action of which is to stimulate the leucocytes to devour 

 the bacteria. 



To conclude this brief account of the reaction of the 

 body to the invasion by foreign substances, we may 

 mention a reaction of a different kind — Anaphylaxis. If 

 5 c.c. of egg-albumen be injected into a guinea pig, no 

 ill effects follow, but on giving a second dose the animal 

 becomes violently ill and usually dies within a minute or 

 two. This curious reaction has the following character- 

 istics : (1) The first dose may be very minute, as httle 



CELL 



Fig. 73. 



