HYPERSUSCEPTIBILITY IN MAN 235 



substances, but the determination of results is by means of the general 

 rather than the local reaction. As with other reactions, controls are a neces- 

 sary part of these tests. The cutaneous test, by which is meant introduction 

 of material into an abrasion, is performed as in smallpox vaccination. Any 

 part of the body may be selected, but we have found the arm most con- 

 venient. Walker advises making small incisions in the skin, deep enough to 

 permit absorption, but not deep enough to cause bleeding. A small dental 

 burr may be used, as in the Schick test. The material is placed on the 

 abrasion or incision and allowed to remain one-half hour. If a powder, a 

 solvent should be added after the powder is placed on the skin. If not com- 

 pletely soluble in water, a weak solution of sodium hydroxide, either o.i per 

 cent., or N/io may be employed, as it does not affect the reaction. Walker's 

 studies show that for detecting hypersensitiveness in cases of asthma, hay 

 fever, etc., the cutaneous test is more delicate and yields fewer false positive 

 reactions than the intracutaneous test. 



The delicacy of these tests is probably greater than that of any 

 other biological reaction. As has been stated, patients sensitive to 

 extracts of hair of an animal may not be sensitive to the serum proteins 

 and vice versa. Very small amounts of antigen suffice to produce reac- 

 tions; alkali metaprotein and pepton from hair and dandruff give 

 reactions commonly in dilutions of I 10,000 and Wodehouse reports 

 one case in which reactions were obtained with dilutions of 1-1,000,000. 

 Clowes reports reaction by means of the ophthalmic test to 0.000,000,05 

 gram pollen. The fact that positive reactions are found with cutaneous 

 tests in individuals whose serum fails to exhibit antibodies by pre- 

 cipitation, agglutination and complement-fixation tests, is a further 

 indication of the delicacy of the reaction. The accuracy of the reac- 

 tions is supported by the beneficial results of specific vaccination or 

 desensitization. The treatment is usually by means of subcutaneous 

 injections of the protein to which the patient is sensitive. In cases of 

 sensitiveness to food products, as well as in other cases, patients may 

 be vaccinated by giving the protein by mouth. In either method the 

 amounts are extremely small, and in most instances the course of treat- 

 ment must be repeated at intervals which may vary from a few months 

 to a year or more. The intracutaneous test appears to be the most 

 delicate in producing local reactions, but unfortunately is more likely 

 to produce confusing traumatic and non-specific reactions to be de- 

 scribed subsequently. Details of treatment are given in numerous 

 articles, such as those of Blackfan, Talbot, Goodale, Berger and others 

 in the recent literature. 



The Reaction. This depends to a certain degree upon the particu- 

 lar cutaneous test employed and the sensitiveness of the patient, but in 

 a general way the description applies to all the methods. An urticarial 

 wheal may appear within a very few minutes and may persist for from 

 several minutes to several hours, elevated, firm, pale and itching. Either 

 with or without this preliminary reaction, the passage of a few hours, 

 six, twelve, twenty-four or more, reveals a local area of inflammation 

 about 10 m.m. in diameter, elevated, papular, red, firm and tender. In 

 severe reactions the area may reach a diameter of several centimetres, 

 may be surrounded by an areola of subcutaneous edema, may show 

 fine punctate hemorrhages and may ultimately show vesicles and 



