H&MOLYSINS. 23 



off as a result of the immunizing process, Ehrlich 

 explains by means of Weigert's Overproduction 

 Theory. Weigert, by his studies in new tissue for- 

 mation, had shown that whenever there is a defi- 

 ciency in the organism, the latter when replacing 

 this is incapable of remaining within bounds, al- 

 ways producing more than is required. Ehrlich 

 points out that owing to the combination of the 

 toxin with the side-chain of a cell, these side-chains 

 are practically lost to the cell ; that the latter now 

 produces new side-chains to replace this loss, but 

 that this production always goes so far as to make 

 a surplus of side-chains; that these side-chains are 

 thrown off by the cell as unnecessary ballast and 

 then circulate in the blood as antitoxin. The same 

 substances, therefore, which when part of the cell 

 combine with the haptophore group of the toxin, 

 enabling that to act on the cell, when circulating 

 free in the blood combine with and satisfy this hap- 

 tophore group of the toxin and prevent the poison 

 from combining with and damaging the cells of the 

 organism. 



Using Ehrlich's comparison, this may be likened 

 to an iron bar within a building which owing to its 

 attraction causes the lightning to strike the build- 

 ing. The same iron bar, however, acts as a protec- 

 tion for the building if it be placed outside of the 

 same. Let us bear this comparison in mind as 

 we glance at the facts in tetanus. This is the easi- 

 est disease in which to study the relation of the 



