OUTLOOK. 681 



small doses. By gradually increasing the dose of this poison to an animal 

 under experiment, we can immunize it, so that it is able to stand relatively 

 large amounts of it. 1 We cannot here go into all the developments 

 arising from these observations, which are so interesting from a biological 

 standpoint. We can state merely that bacteria yield to the body sub- 

 stances which we call toxines. They have a harmful effect upon the normal 

 cell-metabolism. They are, in part, constantly given up by the bacteria, 

 while to some extent the toxines are retained by the bacteria in their cell 

 structure. In the latter case these poisons only become active on the 

 death of the micro-organism. It is questionable whether we are justified 

 in looking upon these two groups of poisons as being unlike. It is possible 

 that the eliminated toxines are the end-products of metabolism. It is just 

 as plausible to believe that we have here a phenomenon which more closely 

 resembles a secretion process. From this point of view it is easier to under- 

 stand why the micro-organisms eliminate such highly complicated sub- 

 stances; while, on the other hand, the conception that the toxines are 

 end-products of metabolism seems doubtful, because we usually find that 

 such substances require but little expenditure of energy for their formation; 

 i.e., they are lower decomposition products. The strictly specific nature of 

 the toxines also harmonizes more readily with the idea of a typical secretion 

 process. In such a case we have to deal with products which are analogous 

 to the ferments. The toxines given off would then correspond to the 

 "unorganized" ferments; those remaining in the cells, to the "organized"' 

 ferments. 



Just as this classification of the ferments is a purely superficial one, and 

 has nothing to do with their nature and their manner of action, so it is 

 perfectly possible that the toxines which are given up freely by the cells 

 and those which are firmly attached to the cells are essentially identical. 

 Again, the comparison of the toxines and ferments is also superficial, and 

 should not prejudice us with regard to the toxines. We do not know 

 anything definite about their nature. They are classed with the proteins, 

 and justly so, for only to this class of chemical compounds can we 

 imagine that such complicated bodies belong. For the same reason we 

 have concluded that the ferments belong to the protein group, being 

 probably transformation products of the cell-proteins. Just as the fer- 

 ments exert a specific action, so the bacterial poisons have well-defined 

 characteristics. We know of poisonous substances which are produced 

 by highly organized plants and by animals the action of which is quite 

 similar to that of the toxines. Thus we have ricin from the castor-oil 

 plant (Ricinus communis), and abrin from the seeds of Jequirity (Abrus 

 precatorius) . Both are extremely poisonous, and an immunity may be 



1 E. Behring: Deut. med. Wochsch. 1890. E. Behring and Kitasato: Ibid. 1890. 



