2-24: WARFIELD T. LONGCOPE AND GEORGE M. MACKENZIE 



that hay fever affects members of families in a proportion which closely ap- 

 proximates the theoretical figures of the Mendelian law and suggests that 

 idiosyncrasies may be inherited as a dominant characteristic. Other ob- 

 servers who have studied this aspect of the question are of much the same 

 opinion and it seems fairly well established now that a condition of the 

 tissues, at least, may be inherited that renders the individual highly 

 prone to the development of hypersensitiveness. The idiosyncrasies them- 

 selves may differ in the different members of the same family and may 

 assume quite different forms of expression. Occasionally, all members of 

 the family may have hay fever, but in some, it may be caused by ragweed 

 and in others by timothy. On the other hand, one member may have hay 

 fever, another horse asthma, and a third egg eczema and urticaria. 



A comparison of the degree of hypersensitiveness which is present in 

 these individuals with that produced artificially by the injection of serum 

 in human beings, or with that obtained experimentally in animals, shows 

 that it is much greater in the former group. Thus, severe or even alarm- 

 ing symptoms may be produced in an asthmatic who is sensitive to the 

 pollen of ragweed or to the epidermal dust of horses, by the subcutaneous 

 injections of such minute quantities as 0.1 c.c. of 1-500 or even 1-10,000 

 dilutions of an extract prepared from ragweed pollen or from the hair 

 and epidermal scales of a horse. And in the same individual, an intracu- 

 taneous injection of a drop of 1-1,000 or even 1-100,000 dilutions of these 

 extracts may call forth an intense local reaction with the formation of 

 an urticarial wheal 2-3 cm. in diameter, surrounded by a zone of erythema 

 58 cm. across. Such responses are almost unknown, either in the arti- 

 ficially sensitized animal or human being, and indicate a degree of re- 

 action in the tissues or body fluids of these hypersensitive individuals 

 which have so far been unobtainable experimentally. 



Observations have shown that in the hypersensitive individual, the 

 reaction may be called forth by the introduction of minute quantities of 

 the material, either to a scarified area of the skin (the cutaneous test), 

 by injection of minute quantities of high dilutions of the protein into 

 the superficial layer of the skin (intradermal test) or by local applica- 

 tions to the mucous membrane of the nose or the conjunctiva. It has been 

 further determined that the degree of reactivity of these tissues may vary 

 to the same protein, in different individuals who are known to be hyper- 

 sensitive to the same protein substances. Those who show the greatest 

 degree of sensitiveness react perhaps violently to the protein. when tested 

 by all methods, those showing a lesser degree of sensitiveness may fail to 

 react when the material is applied to the scarified skin, but respond in 

 a characteristic way when the protein is placed upon the mucous mem- 

 branes or injected into the skin; while finally the slightly sensitive in- 

 dividual reacts solely to the intradermal test. As a rule the local re- 

 actions appear within 15-30 minutes after the application is made, and 



