REACTION OF THE HOST TO INFECTION 



221 



as in the latter class of substances, that is a receptor of the second 

 order with a haptophorous group by which to combine with the 

 foreign cell, and a zymophorous group to bring about its solution, 

 were it not for the observed facts given in the experiment outhned 

 above, which demonstrate the presence of two distinct substances 

 in the cytolytic complex. A new picture is here necessary and 

 it is furnished by making a joint in the arm of the receptor of the 

 second order in which the fermentative property is supposed to 

 reside, separating off the zymophorous group as a separate sub- 



Fjg. 89. — Receptors of the third'-order. (Journ. A. M. A., 1905, p. 1369.) c. 

 Cell receptor of the third order — an amboceptor; e, one of the haptophores of the 

 amboceptor with which the foreign body, /, (antigen) may unite; g, the other hapto- 

 phore of the amboceptor with which complement, k, may unite; h, haptophore of 

 the complement; z, zymophore of the complement. 



stance and leaving a branched figure with two combining or 

 haptophorous elements, one capable of combining with the foreign 

 cell and the other capable of combining with the cytolytic ferment 

 of normal serum and so bringing its action to bear upon that 

 particular cell. The receptor of the third order is called, in 

 accordance with this conception of its relationships, amboceptor, 

 because it acts as a receptor at two points. It is also called 

 intermediary body, immune body and sensitizer. The other com- 

 ponent of the lytic complex, which is thermolabile and which is 



