icio ATOPY 



primary importance of these physical agents as excitants in his cases is revealed by 

 the demonstrated specificity of the susceptibility in the different individuals to a 

 single one of these agencies. Duke states that there is a distinct family history of 

 atopic hypersensitiveness in his cases. 



In this connection may be mentioned the asthmatic symptoms exhibited by 

 practically all individuals coming in sufficient contact with grain infested with the 

 larvae of Pediciiloides ventricosus.'^ The affected individuals suffered also dermatitis, 

 and the infested material possessed immediately irritating properties, as shown by the 

 development of an itching lesion upon first contact with it. It seems at least possible 

 that the asthmatic symptoms in these cases were not an expression of hypersensitive- 

 ness, but the result of direct irritation of the bronchial mucous membrane. Reagins 

 could not be found in the blood of the affected individuals. It is not necessary to con- 

 sider the bronchial shock tissue in these individuals to have been in the atopic state, 

 just as such an assumption is unjustified in the case of normal persons in whom the 

 skin has been passively sensitized to any atopen, and responds, on suitable contact 

 of the excitant, with the local formation of a wheal. 



HOW IS ATOPIC HYPERSENSITIVENESS ESTABLISHED? 



With the foregoing considerations in mind, we are in a position to discuss the 

 question as to the manner in which atopic hypersensitiveness is established in an in- 

 dividual under the controlling influence of heredity.^ It has been thought that the 

 hypersensitive individuals had inherited an abnormal permeability of the surface 

 membranes to unaltered antigens. This idea is confronted with the fact that many 

 persons became sensitive to only one member of a group of similar excitants (a single 

 pollen atopen or a single animal or vegetable protein). In order to make the theory of 

 abnormal permeability conform with this fact, it would have to be assumed that the 

 abnormal permeability was specific; for this assumption there is no evidence. More- 

 over, there is ample evidence of a normal permeability of the gastro-intestinal tract 

 to various common proteins (milk, egg, fish, pollen, nut). With the use of his ingen- 

 ious method of skin sensitization to several proteins, Walzer-' has demonstrated a per- 

 meability of the gastro-intestinal tract to the unaltered antigens in about go per cent 

 of normal individuals. These observations show that practically all people are equally 

 exposed to parenteral and prolonged contact with the atopic excitant, and that this 

 factor cannot therefore be a determining one in the establishment of atopic hyper- 

 sensitiveness. This fact leads us inevitably to the conclusion that the establishment 

 of the hypersensitiveness is determined wholly by heredity, and this is further sup- 

 ported by the common observation that the subcutaneous or intravenous injection of 

 large quantities of foreign protein (horse serum) does not result in the establishment 

 of an atopic hypersensitiveness. In view of the numerous instances of hypersensitive- 

 ness developing to a single substance or group of substances, and, in view of the dem- 

 onstration by Cooke and his associates'* of the controlling influence of heredity upon 



' Ancona, G.: Sperimenlale, 76, 270. 1922; Grove, E. F.: J. Immunol., 12, 263. 1926. 



^ Coca, A. F.: J. Lab. 6° Clin. Med., 12, 1135. Sept., 1927. 



3 Walzer, M.: J. Immunol., 13, 143. 1927. 



"I See Coca, A. F.: Tice's Practice of Medicine, i, 107. llagerstown, Md.: W. F. Prior Co., 

 1920; Spain, W. C, and Cooke, R. A.: loc. cit. 



