The question of any diagnosis centers about either clinical judgment or some laboratory test. In the past, many cases of streptococcus infection other than scarlet fever have been labeled as scarlatina by physicians, because there was no definite method of making an absolute diagnosis. If a person had a rash associated with a sore throat, and the rash looked somewhat similar to that of scarlet fever, then for all practical purposes the patient was considered as having the disease. This was the stage when Schultz and Charlton first described their phenomenon. Briefly, the intradermal injection of a certain amount of convalescent scarlet fever serum into a patient with a rash of acute scarlet fever caused local blanching or local cure at the site of injection. If the serum of a person suspected of having scarlet fever was injected into the skin of a patient with acute scarlet fever with a