SPECIAL PROPERTIES OF BLOOD SERUM. 277 



medium where these complexes are, present the immune body 

 attaches itself to the haptophorous group of the cell. In this 

 condition no action follows immediately ; but the immune com- 

 plex has itself two haptophorous groups or side chains, 

 through one of which the union with the bacterial cell is ef- 

 fected, while with the other it joins on to the addiment or 

 complement through its haptophorous group. In this way the 

 complement, w r hich alone is inactive or unable to attack the 

 cell, is brought into the immediate neighborhood of the latter, 

 where its proteolytic efforts are more effective. Every fresh 

 normal serum seems to have present enough of the complement 

 groups; the question of destroying the invading cell depends 

 then on the number of immune or intermediary groups in the 

 field. Another part of the Ehrlich theory attempts to account 

 for these. 



The Immune Group. Ehrlich traces the development of 

 the immune body to the spontaneous effort on the part of the 

 cell to protect and regenerate itself in case of partial destruc- 

 tion. The various cells of the body exist in a kind of equilib- 

 rium with each other. An injury to one, that is the loss of 

 some of its side chains, immediately leads to an effort at com- 

 pensation. The hyperplasia observed in an organ may extend 

 to the single cells and in consequence of this we have over- 

 compensation. The cell's efforts at regeneration lead to the 

 production of more side chains than are actually necessary and 

 some of these combine with the aid of their receptor groups 

 with toxin or with complement. Many are formed in excess 

 and are thrown off into the circulation. These free receptors 

 constitute the various anti or immune bodies. Combining 

 with complement groups they form the true cytotoxins. The 

 larger the number of free receptors 'thrown off into the blood 

 by the over-compensating efforts of the attacked cells the 

 stronger is its cytotoxic or antitoxic character since these re- 

 ceptors hold either the toxin or foreign cell and thus protect 

 the parent native cell from attack or destruction. 



The fundamental point then in the Ehrlich theory of serum 



