546 IMMUNOLOGY 



point of infection is to a certain extent in proportion to the de- 

 gree of local tissue injury, e.g., the staphylococcus produces a 

 great deal of local tissue injury and is also fixed more extensively 

 than other organisms producing less local necrosis. 



Lurie states that the guinea pig develops more allergy to the 

 tubercle bacillus than the rabbit. When tubercle bacilli are 

 introduced into its tissues (agar-bacteria implantation) there is 

 both a greater allergic response and a greater local fixation of 

 bacteria. In the allergic inflammation of the guinea pig the fibrin 

 network is finer, more compact, and tliere is a plugging and oc- 

 clusion of tlie lymphatics. In the rabbit similarly treated, the 

 fibrin network is coarser and the lymphatics remain open. These 

 findings may account for the apparent contradictory conclusions 

 drawn from experimental work mentioned earlier in this chapter. 

 Some of the work on experimental allergy and immunity was done 

 on rabbits and some on guinea pigs. 



Cannon's and Hartley's Work on Allergy and Immunity'. — 

 Cannon and Hartley rendered rabbits allergic to egg albumen and 

 then injected a mixture of egg albumen and virulent pneumo- 

 cocei. The allergic inflammation did not protect the rabbits from 

 a fatal pneumococcus infection. The organisms "grew profusely 

 in the areas of allergic inflammation and spread evenly through the 

 field of inflammation. While phagocytosis was moderately active, 

 it did not modify the course of infection either in time or degree. ' ' 

 This was in marked contrast to the phenomena observed in rabbits 

 allergic to egg albumen but immune to the pneumococcus. In these 

 rabbits the organisms grew profusely for a time but they became 

 swollen, developed in isolated colonies, many became gram-negative 

 and tended to remain localized. These experiments apparently 

 show that, for the pneumococcus infection in rabbits, allergic in- 

 flammation without the aid of immunity factors such as antibodies 

 cannot be regarded as a defensive mechanism. 



Discussion. — From a consideration of the results of Smith, 

 Lurie, and Cannon and Hartley presented in the preceding para- 

 graphs the following conclusions seem to be justified : 



1. That as the body becomes more immune to the tubercle 

 bacillus there is a diminishing tendency for any visible re- 

 sponse. There is no evidence of allergy where complete im- 

 munity exists. 



