176 LOCAL TLSSHE REACTIVITY 



a mild inflammatory icaclion. riic second injection ])r()iiti,lit al)oiit 

 a ])i()n()inuc'd edema. I listolo^ically, there was a dittiise and dense 

 leiieocytic inldiialion witli Inalini/ation ol the collagenous fibers 

 aeeomj)anied by occasional small areas ol extravasation. There 

 ^vas no damage to the blood \esi;els. Leucocytes showed no signs 

 ol' necrcibic:)sis. According to this aiithoi, it was note^v()rthy that 

 leucocytes infiltrating the pre})ared skin site following the in- 

 travenous injection underwent comjilete necrobiosis. He drew 

 attention to the fact that the intravenous injection of the toxic 

 substances prc:)duced a massive destruction of leucocytes in the 

 capillaries of the liver. Tt was clear, therefore, that the leucocytes 

 thus injured showed a very low degree of resistance ^vhen they 

 reached the prepared skin site. 



In recent .experiments of Gerber (ig^^Gc/) , a rabbit received in- 

 tradermally 0.25 c.c. of B. typhosus filtrate equivalent to 1(87 re- 

 acting imits. Twenty-fotu- hoins later a similar dose Avas injected 

 into the same site and the skin removed 4 hoins later. In the gross, 

 there Avas an area of edema 2.5 cm. in diameter of a deep red color. 

 No gross hemorrhages were seen. Microscopic examination re- 

 vealed a severe degree of inflammation characterized by marked 

 edema and extensive polymorphonuclear leucocytic infiltration. 

 There was marked perivasctdar infiltration and at times the cells 

 infiltrated the entire vessel wall. Ho^vever, no thrombi were pres- 

 ent. Hemorrhage was likewise absent. Many of the capillaries 

 were dilated and engorged. Small foci of necrosis were scattered 

 in the subcutaneous tissue. As was seen from the description of 

 the histology of the phenomenon, the absence of thrombosis and 

 hemorrhage readily serves to distinguish this picture from that 

 seen in the typical reaction follo^ving the intravenous injection 

 of reacting factors. It must be emphasized that the amoiurt of 

 filtrate employed in Gerber's experiments for repeated intrader- 

 mal injection ^vas many times greater than that used to obtain 

 the phenomenon. In the gross there is also a sharp difference 

 between the appearance of the reaction following repeated intra- 

 dermal injections into the same site and the typical phenomenon. 



In order to determine ^vhether some sort of a modihcation 

 wotdd enable the second intradermal injection to elicit a typical 

 reaction, the follo^^■ing experiments uere done by me: 



Each experiment ^vith a given substance was performed in 6 rab- 

 bits. Three sites were prepared by simultaneous intradermal in- 

 jections of 0.25 c.c. of B. typJiosus "agar washings" filtrates. 



