Dr.Head has recently examined the children of households in which there was open tuberculosis in some member of the household.

By open tuberculosis is understood a case from which bacilli are being discharged.

He found with scarcely an exception that all the children in such families showed evidences of infection.

The detection of slight degrees of tuberculous infection is now made easy by certain skin reactions on inoculation of the skin with a substance derived from the tubercle bacilli.

Such latent infections may never become active and in the majority of cases do not.