INTRODUCTION 23 



only ^vith })neumococcus preparations and could not be repro- 

 duced at will. The individual susceptibility of rabbits apparently 

 ^vas an important factor. Ihiforttniately, the preparations were 

 not tested for primary pneumococcus purpurogenic substances 

 of Julianelle and Reimann (1926, 1927) . It is quite possible that 

 pneinnococcus material employed in my experiments contained 

 the purpurogenic factors in addition to the active principles of 

 the phenomenon. This assiunptic:)n is supported by the fact that 

 lesions of the type described were not obtained by me thus far 

 with any other bacterial preparations, julianelle and Reimann 

 found that extracts of strains of Staphylococcus aureus, Strepto- 

 coccus viridaus, Streptococcus Jieiuolyticus, B. coli, and the men- 

 ingococctis do not contain the pinpurogenic factors. 



The experiments ^vith pneumococcus material described here 

 are instructi\e for pinposes of differentiation of the lesions of 

 the phenomenon from possible superadded primary lesions 

 elicited by certain purpurogenic factors. Lesions at sites prepared 

 with 0.25 c.c. which exceed 5 x 5 cm. and also lesions spreading 

 over a large area and appearing of equal intensity at the prepared 

 site, as well as beyond it, shoidd be considered as those compli- 

 cated by some additional purpm'ogenic factors. 



The work of Dman-Reynals (19-^2, 1933) has recently demon- 

 strated that invasive strains of staphylococcus and streptococcus 

 contain a soluble factor which markedly increases tissue perme- 

 ability and enhances the infection produced by these organisms, 

 by other bacteria and by vaccine virus as well. The non-invasive 

 strains of the same species of staphylococci and streptococci do 

 not contain this factor. Reynal's spreading bacterial factors are, 

 ho'wever, apparently absent from the meningococcus, according 

 to this author, and from B. coli, B. typJwsus ctdture fdtrates, 

 according to my o^vn observatic:)ns and, therefore, j^resent no con- 

 cern in the studies of the phenomenon of local skin reactivity to 

 bacterial fdtrates. Their role in the phenomenon of local skin 

 reactivity to streptococcus remains to be determined. 



THE QUANTITATIVE ESTIMATK^NS OF POTENCY OF ACTIVE PRINCIPLES 



It was realized by me early in the ^vork that quantitative esti- 

 mations of potency of active principles are essential for studies 

 on various aspects of the phenomenon. The methods described 

 below% as illustrated by typical experiments, were employed in 

 these studies. 



