268 ANAPHYLAXIS 



enzymes are not used up rapidly enough since the products 

 of the bacillus are secreted slowly in such cases. Hence 

 excess of enzyme is free in the blood and the injection of 

 the tuberculin meets it there and a vigorous reaction results. 

 In old, far-advanced cases, no reaction occurs, because the 

 enzymes are all used in decomposing the large amount of 

 tuberculous protein constantly present in the blood. The 

 fact that an animal which has once reacted fails to do so 

 until several months afterward likewise depends on the fact 

 that the excess enzyme is used in the reaction and time must 

 elapse for a further excess to accumulate. 



The anaphylactic reaction has been made use of in the 

 identification of various types of proteins and is of very 

 great value since the reaction is so delicate, particularly 

 when guinea-pigs are used as test animals. Wells has 

 detected the 0.000,001 gm. of protein by this test. It is evi- 

 dent that the test is applicable in medicolegal cases and in 

 food examination and has been so used. 



Summary. 



The discussion of "immunity problems" in the preceding 

 chapters serves to show that protection from disease either 

 as a condition natural to the animal or as an acquired state 

 is dependent on certain properties of its body cells or fluids, 

 or both. The a,ctual factors so far as at present known may 

 be summarized as follows: 



1. Antitoxins which neutralize true toxins, shown to exist 

 for very few diseases. 



2. Cytolytic substances which destroy the invading organ- 

 ism: in reality two substances; amboceptor, which is specific, 

 and complement the real dissolving enzyme. 



3. Phagocytosis or the destruction of the invading organ- 

 isms within the leukocytes. 



4. Opsonins which render the bacteria more readily taken 

 up by the phagocytes. 



5. Enzymes other than complement possibly play a part 

 in the destruction of some pathogenic organisms or their 

 products. This remains to be more definitely established. 



