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SCIENCE 



[N. S. Vol. XXVII. No. 695 



typhoid and colon bacilli this is followed 

 by a definite immunity. In the ease of 

 anthrax, however, immunity does not fol- 

 low hypersusceptibility to the anthrax pro- 

 tein. We are therefore not dealing with a 

 general law applicable to all infections, but 

 with certain limitations as in the case of 

 antitoxic immunity. 



Hypersusceptibility and Immunity: Victor 

 C. Vaughan. 



In order that I may be correctly under- 

 stood I wish to state at the beginning that 

 in my opinion the mechanism of immunity 

 to all infections and intoxications is not 

 the same and the time has come when it is 

 well for us to distinguish between the dif- 

 ferent forms of immunity. I believe that 

 there is already sufficient ground to justify 

 us in holding that there are at least three 

 forms of immunity and these I would 

 designate as follows: 



1. Antitoxin Immwvity. — The poison to 

 which this form of immunity may be 

 secured are the venom of serpents, the 

 vegetable poisons, abrin and ricin, and the 

 toxins of bacillus diphtheria, b. tetanus 

 and b. botulinus. Possibly others may be 

 added to the list. These poisons certainly 

 belong to a distinct group. They resemble 

 ferments in three striking particulars: 

 (a) in aqueous solution they are destroyed 

 by a temperature of 100° or less; (h) they 

 are active in solutions so dilute that they 

 do not respond to the three most char- 

 acteristic proteid color reactions, the 

 biuret, Millon and Molisch tests; '^c) ani- 

 mals treated with successive doses at short 

 intervals develop anti-bodies. For the 

 present at least Ehrlich's theory must be 

 regarded as the most satisfactory explana- 

 tion of this form of immunity. There is 

 no proof, so far, that either phagocytic 

 action or proteid cleavage has anything to 

 do with the production of this form of 

 immunity. 



2. Phagocytic Immunity.— Hhis form of 

 immunity has been most thoroughly 

 studied with the cocci, and as we are to 

 have two papers on it to-day I will refrain 

 from expressing any opinion of my own on 

 the subject. 



3. Lytic Immunity. — This is generally 

 designated as bactericidal or bacteriolytic 

 immunity, but there is serious objection to 

 the employment of either of these terms, for 

 the following reasons: (a) bacterial pro- 

 teids are not the only proteids that may be 

 and are split up in the animal body. Most 

 foreign proteids when introduced into the 

 circulation directly and without previous 

 subjection to the digestive juices undergo 

 specific proteolysis, and this is true whether 

 these proteids are living or dead. (&) The 

 cleavage of poisons in the body is probably 

 not confined to those of proteid composi- 

 tion, (c) The term bactericidal is inap- 

 propriate because the bacteria may be so 

 altered chemically that they are robbed 

 in part or wholly of their harmful 

 properties and still are not killed. Ex- 

 amples of the persistence of specific bac- 

 teria in the body after recovery from the 

 disease are well known and immunity to 

 disease may coexist with the specific bac- 

 teria of that disease still living in the body. 

 The bacterial proteid owes its poisonous 

 action to its molecular structure and this 

 may be so modified as to render the organ- 

 ism a comparatively harmless guest with- 

 out destroying its life, {d) The term bac- 

 teriolysis is certainly inappropriate, first 

 because all these poisons are not bacterial 

 and second because the word bacteriolysis 

 means that the bacterial cell is destroyed, 

 and we have just seen that this does not 

 happen in all cases. In view of the facts 

 here briefly condensed I prefer the word 

 "lytic" to designate this form of im- 

 munity. I am not altogether satisfied with 



