614 



VETERINAKY PHYSIOLOGY 



to the complement before it can act. The figure may help to 

 explain this (fig. 234). 



3. Cytotoxins. — Similar anti-bodies, acting upon the cells 

 of the animal body, may be produced by injecting the particular 

 kind of cell into an animal of another species. Thus, if human 

 blood be repeatedly injected into a rabbit, the serum of the 

 rabbit's blood becomes hcemolytic — i.e. acquires the power of 

 dissolving the erythrocytes in human blood. In this case too, 

 the immune body requires the presence of a complement, 

 readily destroyed at a comparatively low temperature, to enable 

 it to act (see p. 486). 



If such hgemolytic serum be injected into another animal 

 an anti-hcemolysin may be developed — a body which will 



V 



SC 



Fig. 233.— To illustrate the For- 

 mation of Side-chains or Recep- 

 tors, SC, by which the toxin mole- 

 cules, T, are either anchored 

 to the cell or neutralised. 

 When the side-chains are set 

 free an anti-toxin is formed. 



Fig 234.— To illustrate the 

 Anchoring of the Anti- 

 body or Amboceptor, a, 

 to tlie cell by a side-chain 

 or receptor, sc, and the 

 action upon it of comple- 

 ment, com. 



antagonise the action of the hsemolysin. Possibly this is a 

 body which links with the amboceptor to prevent its linking 

 to the complement. 



4. Precipitins. — By the injection of the proteins of the blood 

 of any particular animal into an animal of another species, a 

 serum is developed which, in association with the proteins of 

 the blood of the first species, forms a precipitate. This action is 

 specific, unless in the case of closely allied species when it may 

 occur to a slight extent. 



5. Agglutinins. — These constitute another group of anti- 

 substances. They may be developed towards bacteria, erythro- 



