18 PROPERTIES OF ELEMOLYTIC SERA 



the cell receptor sensitizes the immune-body with a corre- 

 sponding result. Sensitizing thus means only the produc- 

 tion of a combining affinity in a molecule which otherwise 

 does not possess it ; and the increase of combining affinity 

 already present in small degree without the presence of an 

 immune-body, is also a part of sensitizing action. 



We have thus to consider the evidence for the direct 

 union of complement and immune-body. It may be stated 

 at the outset that this appears to us not to be of conclusive 

 nature. As was first shown by Ehrlich and Morgenroth, 

 immune-body may be separated from a mixture containing 

 complement by adding the homologous red corpuscles at 

 C., the complement not entering into combination at 

 that temperature. Thus immune-body appears to exist 

 separately in the mixture. Ehrlich, however, suggested that 

 the two substances really form a loose union at a higher tem- 

 perature, say 37 C. Certain recent experiments carried out 

 by Dr. Browning and myself lend, however, no support to 

 such a view. It is shown below (p. 90) that on filtering 

 fresh serum through a Berkefeld filter, complement is in 

 great part retained ; the first few cubic centimetres which 

 pass through contain almost no complement. On the other 

 hand, immune-body passes through the filter practically 

 unaltered. Now, if complement combines with immune- 

 body at 37 C., and if complement is retained by the filter, 

 then on a mixture of the two being filtered at 37 C. the 

 immune-body in combination with complement should also 

 be retained by the filter. We have found, however, that 

 such is not the case in the circumstances mentioned as 

 much immune-body passes through when mixed with 

 complement as when it is filtered alone. These experiments 

 accordingly lend no support to the view that complement 

 unites directly with immune-body at 37 C. 



The Neisser-Wechsberg phenomenon has also been used 

 in support of the amboceptor theory. The essence of this 



