The Biological Significance of Anaphylaxis. 557 



primarily affected. They resemble closely the characteristic types of action, 

 on these same species, of a large class of naturally poisonous proteins, protein 

 cleavage products, and organ extracts, and of the organic base amino-ethyl- 

 glyoxaline (histamine). Blood in clotting acquires toxic properties of a 

 similar type. The complex can be analysed into an action mainly on two 

 tissues — stimulation of plain muscle and poisoning of the vascular endo- 

 thelium. These two effects appear with different relative prominence in the 

 different species. 



Several theories have been put forward to explain the anaphylactic 

 phenomena. It is agreed by all that anaphylaxis is due to the presence of a 

 specific antibody of the precipitin type. 



1. It is supposed that the formation of the complex of antigen and antibody 

 in the blood leads to a rapid digestive hydrolysis, with the liberation of 

 poisonous cleavage products. 



2. It is supposed that the union of antigen and antibody produces a 

 disturbance in the equilibrium of the blood colloids, initiating pre-coagulation 

 changes and rendering the blood toxic to the tissues. 



3. It is supposed that the difference between anaphylaxis and immunity is 

 due to the different distribution of antibody between the cells of the tissues 

 and the blood-plasma. The occurrence of the reaction between antigen and 

 antibody in the tissue cells is regarded as the cause of the anaphylactic 

 symptoms. Evidence in favour of the last hypothesis is afforded by the 

 reaction of isolated plain muscle from (actively or passively) anaphylactic 

 and immune guinea-pigs. 



The meaning of the " specificity " of anaphylaxis and immunity is discussed, 

 in the light of the recent work by Dakin and Dudley, which gives the first 

 hint of the difference in molecular pattern between corresponding proteins 

 from different species. 



There has been a general tendency to interpret the anaphylactic reaction 

 in terms of the action of poisonous cleavage products of proteins, explaining 

 the symptoms by assuming the formation of the products having this type of 

 action. It is suggested that the true order of interpretation may be in the 

 inverse direction ; that more is known of the nature of the change in the 

 cells which results in the anaphylactic shock than of the mode of action of 

 the substances which produce analogous symptoms in the normal animal. 



Further study of the anaphylactic reaction may throw light on the action 

 of naturally poisonous protein-derivatives and drugs, and on the intimate 

 physiology of plain muscle fibres and other cells. 



