NATURE OF THE ACTIVE PRINCIPLES 31I 



or not. Conversely, the extracellular nature of the active principles 

 of the phenomenon, the regularity of the effect (100 per cent with 

 certain microorganisms if sufficient doses are used) , consistent 

 neutralization in multiple proportions and high antigenicity, all 

 these properties considered together differentiate them sharply 

 from the endotoxins just described. 



RELATION OF THE PHENOMENON-PRODUCING POTENCY TO 

 LETHAL EFFECT OF CULTURE FILTRATES 



Apart from endotoxins, many of the bacteria in wiiich no exo- 

 toxins were hitherto clearly demonstrated produce certain ill 

 defined soluble lethal factors which were termed by Zinsser 

 x-substances and described by Parker (1919) , Zinsser (1920) , and 

 Zinsser, Parker and Kuttner (1920-21). The x-substances were 

 obtained from B. iufiuenzae and several other pathogenic and non- 

 pathogenic bacteria and ^^ere present in young agar culture Avash- 

 ings and filtrates of young broth cultures. Rabbits were more sus- 

 ceptible than guinea pigs. The substances killed acutely after a 

 short but definite incubation period and produced no specific 

 pathologic effect. These authors could not determine the antigenic 

 properties of the x-substances because of fluctuations in suscepti- 

 l)ility of animals and the fact that immunized animals died from 

 cachexia during the process of active immunization. These authors 

 thought that the x-substances cannot be dismissed merely as split 

 products as they do not appear to be derived from the substances 

 of the bacterial cells. 



The "agar ^vashings" filtrates in amounts sufficient to elicit the 

 phenomenon of local skin reactivity, produce in a high percentage 

 of rabbits symptoms of general intoxication very similar to those 

 observed by Zinsser Avith x-substances. The follo'wing detailed 

 description of this effect is given by Stolyhwo (1935) . The symp- 

 toms can be grouped as those of acute intoxication, ^vhich kill 

 the rabbits within a few hours following the injection; and those 

 of subacute intoxication or protracted intoxication which elicit 

 a severe cachexia and kill the rabbits ^vithin t^vo Aveeks follo^ving 

 tlie injection. In the form of acute intoxication the intravenous 

 injcc tion produces prostration, chills and convulsions Avithin a fe\\' 

 minutes following the injection. The respiration becomes alter- 

 nately short and prolonged. Moist rales can be heard in the lungs. 

 The frequency of the heart beat shortens in some cases in 

 otiiers, arhythmia takes place. In 50 per cent of all the rabbits there 



