16 VACCINE AND SERUM THERAPY. 



the individual follows When, however, the toxins do not anchor 

 enough receptors or are not potent enough to destroy the cell 

 and the organism, immunity results or follows. 



In 1896, Weigert advanced the hypothesis that when tissue 

 is lost the regeneration that follows is not only sufficient to restore 

 the amount of tissue lost, but actually results in overproduction 

 of this tissue. This process is observed in the over-production 

 of segments in reptiles and of cell proliferation in granulating 

 wounds in man and the animals. Ehrlich assumes that when 

 the toxins combine with the receptors of the cell, the receptors 

 are lost to the cell and as a result the cell is stimulated to repro- 

 duce the destroyed receptors. The process does not stop, how- 

 ever, when all lost receptors have been reproduced, for more re- 

 ceptors will be produced than were anchored by the toxins. The 

 excessive production of receptors as a .result of the stimulus fol- 

 lowing the anchorage of the receptors by toxins, Ehrlich assumes, 

 leads to a disturbance of the equilibrium of the cell. As a result 

 of this, the surplus receptors are thrown off and constitute what 

 is known as the anti-body. This process can be actually ob- 

 served in the lower animals in which extra parts, produced 

 as a result of destruction of some parts, are cast off or lost. 



The principal function of all receptors and side chains is to 

 provide for the nutrition and metabolism of the cells. Receptors, 

 and hence immune bodies, however, are not all of the same com- 

 position or even of the same general structure. In order to ex- 

 plain the different functions and actions of different immune 

 bodies, Ehrlich has assumed that the receptors may be of simple 

 constitution and structure or they may be complex. Any cell 

 of the body may have large numbers of the same and different 

 kinds of receptors. Ehrlich divides this large number of receptors 

 into three orders. 



RECEPTORS OF THE FIRST ORDER. 



These are receptors that are of relatively simple constitution 

 and structure and combine with substances that can be easily 

 and readily anchored. Bacterial toxins anchor receptors of 

 this order. The receptor here consists of only one haptophore, 

 or combining group, which combines directly with the hapto- 

 phore group of the bacterial toxin. This order of receptors and 



