But not all of the dread of diphtheria went under its own name. Most of us can still remember when the commonest occupant of the nursery shelf was the bottle of ipecac or soothing-syrup as a specific against croup. The thing that most often kept the mother or nurse of young children awake and listening through the night-watches was the sound of a cough, and the anxious waiting to hear whether the next explosion had a "croupy" or brassy sound. It was, of course, early recognized that there were two kinds of croup, the so-called "spasmodic" and the "membranous," the former comparatively common and correspondingly harmless, the latter one of the deadliest of known diseases. The fear that made the mother's heart leap into her mouth as she heard the ringing croup-cough was lest it might be membranous, or, if spasmodic, might turn into the deadly form later. To-day most young mothers hardly know the name of wine of ipecac or alum, and the coughs of young children awaken little more terror than a similar sound in an adult. Croup has almost ceased to be one of the bogies of the nursery. And why? Because membranous croup has been discovered to be diphtheria, and children will not develop diphtheria unless they have been exposed to the contagion, while, if they should be, we have a remedy against it. He was a bold man who first ventured to announce this, and for years the battle raged hotly. It was early admitted that certain cases of so-called membranous croup in children occurred after or while other members of the family or household had diphtheria; and for a time the opposing camps used such words as "sporadic" or scattered croup, which was supposed to come of itself, and "epidemic" or contagious croup, which was diphtheria. Now, however, these distinctions are swept away, and boards of health require isolation and quarantine against croup exactly as against any other form of diphtheria. Cases of fatal croup still occasionally occur which cannot be directly traced to other cases of diphtheria, but the vast majority of them are clearly traceable to infection, usually from some case in another child, which was so mild that it was not recognized as diphtheria until the baby became "croupy" and search was made through the family throats for the bacilli.