ALLERGIC REACTIONS IN TYPHOID FEVER 651 



and ether, drying in a vacuum, and suspending the resulting powder in 

 phenolized normal salt solution which was injected intracutaneously 

 and applied cutaneously; a control powder was prepared from broth 

 and used in the same manner. With this skin test Gay and his associates 

 have studied the relative value of various vaccines and regard the ana- 

 phylactic reaction as indicative of a state of immunity. Nichols 1 has 

 questioned the value of the anaphylactic skin test as an index of im- 

 munity and regards the reaction as indicating nothing more than sensi- 

 tization to typhoid protein, which is apparently less lasting and less 

 specific than the true immunity to this infection. He bases this opinion 

 on the fact that in his experience the typhoidin skin test gave fewer 

 positive reactions (75 per cent.) than generally expected, as about 90 per 

 cent, of persons who have had typhoid fever are immune for many years 

 or even for the balance of life. Furthermore, according to Nichols, 

 experience has shown that protection following typhoid fever is of longer 

 duration than is indicated by the typhoidin test, and while a large per- 

 centage of persons who have had typhoid fever or have been immunized 

 with typhoid vaccine react to paratyphoidin, recent experiences and 

 statistics, particularly in Europe, have indicated that these persons are 

 not immune to paratyphoid fever. Kilgore 2 has reported favorably upon 

 the value of the typhoidin cutaneous test; Austrian and Bloomfield 3 

 found that the test failed to furnish data by means of which it was pos- 

 sible to differentiate between those who had neither typhoid fever 

 nor had received the vaccine and those who had either had the disease 

 or had been immunized. 



In our own experience 4 powdered typhoidin and its control produced 

 severe reactions when injected intracutaneously in doses of 0.0005 to 

 0.001 mgm.; these reactions and particularly that produced by the 

 control rendered the reading and interpretation of the test quite difficult 

 and subject to much error. Cutaneous anaphylaxis to typhoidin was 

 found apparently to persist for a longer time among those who have had 

 typhoid fever than among those actively immunized with the vaccine. 

 Among the latter the highest percentage of reactions was found during 

 the first year following immunization. The test was advocated as a 

 means of determining whether or not a person possesses immunity to 

 typhoid fever either acquired by recovery from the disease or by arti- 



1 Jour. Exper. Med., 1915, 22, 780. 



2 Archiv. Int. Med., 1916, 17, 25. 



3 Archiv. Int. Med., 1916, 17, 663. 



4 Jour. Immunology, 1916, 1, 409. 



