304 LOCAL TLSSUE REACTIVITY 



precipitation l)y means ol metal salts. The most siiecesslul recent 

 attemj)ts ol jjinificatioii of diphtheria toxin were those of Locke 

 and Main by acid precipitation at the isoelectric point and by 

 Eatc:)n by precipitation with aluminimi anmionimn sulphate and 

 cadmium chloride. Eaton obtained jDurihed toxins containin» 

 0.0005 "1,^111- nitrogen per Lf unit and 0.00002 mgm. per Mid. 

 The results seem to suggest that the toxic antigenic and serolog- 

 ical properties of diphtheria toxic filtrates are due to a single 

 j)rotein-like siU)stance. The possibility that diphtheria toxin is a 

 comj)lex carbohydrate or lipoid or some simpler organic sub- 

 stance is excluded inasmuch as several stages of purification in- 

 volving different protein precipitation reactions could not sepa- 

 rate the protein from the toxin. Dernby showed that the fatty 

 substances of the bacilli or of the toxin broth are devoid of toxic- 

 ity. True toxins are easily digested by proteolytic enzymes. Al- 

 though no dehnite information exists as yet there is suggestive 

 evidence that the toxic complex is approximately of the same size 

 as j)roteoses and peptones. According to Rotix and Yersin diph- 

 theria toxin diffuses through parchment membranes but it is re- 

 tained in colloidion sacs. Dernby (1926), and Walbum (1929) 

 carried out a series of experiments on dialysis of diphtheria toxin 

 under constant pressure and compared the diffusibility of the 

 toxin with Witte's peptone. The toxins diffused through these 

 membranes with the same speed and under the same pressure as 

 Witte's peptone. Glenny and Walpole (1915) successfully used 

 dialysis for purification and concentration of diphtheria and 

 tetanus toxins. 



Although the exact knowledge concerning the physico-chemical 

 and chemical properties of the active principles of the phenom- 

 enon is not available as yet, a close similarity with the true toxins 

 may l)e seen. 



In recent experiments active j)rinciples of the phenomenon 

 derived from various microorganisms were dialyzed through "Cel- 

 lophane" l)ags. The extent of retention of the active principles 

 inside of the bags and also the extent of purification of the bac- 

 terial filtrates were estimated by means of accurate quantitative 

 determinations of reacting potency of the materials. The experi- 

 ments proved beyond doubt that the active principles of the 

 phenomenon are consistently retained inside of "Cellophane" 

 bags. This, then, offers an opportunity to obtain a significant 

 ptnification of the filtrates. The })urihcation thus effected 



