Chicken pox is the mildest of eruptive diseases. It has no relation to smallpox, so that the theory sometimes held, that an attack of chicken pox prevents any attack of smallpox later, is a mistake. Instances are on record where a person has had both diseases almost at the same time. The appearance of the eruption is the characteristic feature of this disease, and it is so well distinguished that there is no danger of failing to recognize it. It is not common in grown people, and while it should not arouse suspicion in children, it is so uncommon in adults that a suspected case is probably a mild case of smallpox, and should always be quarantined as such. With children, the accompanying cold and fever is often very mild, so that the appearance of the rash is the first and only symptom of the disease. The eruption is a progressive thing, each day's crop coming to full bloom and dying out as the next day's crop develops. This is, by the way, a distinguishing characteristic of this disease, differentiating it from smallpox where the pustules are more persistent and where the breaking out is more general. The pustules are sometimes extremely irritating, and it is very hard to keep children from scratching, the results of which may leave deep scars and so should be avoided. An antiseptic ointment should be used as with scarlet fever and measles, carbolized vaseline being suitable, although sometimes a strong solution of soda is substituted. It is not common to disinfect in chicken pox to the same extent as in the other diseases, the contagion being apparently in the air rather than in clothing and short lived. In New York State, in 1908, no deaths are recorded from chicken pox, and it is because of this lack of fatal results that the disease is regarded so indifferently and no particular pains taken to prevent its spread. CHAPTER XIX _PARASITICAL DISEASES (MALARIA, YELLOW FEVER, HOOKWORM, BUBONIC PLAGUE, AND PELLAGRA)_ _Malaria._