Unlike the other diseases of childhood, also, one attack confers no positive immunity for the future, although it greatly diminishes the probabilities; and, further, while adults do not readily or frequently catch the disease, yet when they do the results are apt to be exceedingly serious. Indeed, we have practically come to the conclusion that one of the main reasons why adults do not develop diphtheria so frequently as children, is that they are not brought into such close and intimate contact with other children, nor are they in the habit of promptly and indiscriminately hugging and kissing every one who happens to attract their transient affection, and they have outgrown that cheerful spirit of comradeship which leads to the sharing of candy in alternate sucks, and the passing on of slate-pencils, chewing-gum, and other _objets d'art_ from hand to hand, and from mouth to mouth. Statistics show that of nurses employed in diphtheria wards, before the cause or the exact method of contagion was clearly understood, nearly thirty per cent developed the disease; and even with every modern precaution there are few diseases which doctors more frequently catch from their patients than diphtheria. It is a significant fact that the risk of developing diphtheria is greatest precisely at the ages when there is not the slightest scruple about putting everything that may be picked up into the mouth,--namely, from the second to the fifth year,--and diminishes steadily as habits of cleanliness and caution in this regard are developed, even though no immunity may have been gained by a mild or slight attack of the disease. The tendency to discourage and forbid the indiscriminate kissing of children, and the crusade against the uses of the mouth as a pencil-holder, pincushion, and general receptacle for odds and ends, would be thoroughly justified by the risks from diphtheria alone, to say nothing of tuberculosis and other infections. In addition to being almost the only common disease of childhood which is not mild and becoming milder, diphtheria is unique in another respect, and that is its point of attack. Just as tuberculosis seizes its victims by the lungs, and typhoid fever by the bowels, diphtheria--like the weasel--grips at the throat. Its bacilli, entering through the mouth and gaining a foothold first upon the tonsils, the palate, or back of the throat (pharynx), multiply and spread until they swarm down into the larynx and windpipe, where their millions, swarming in the mesh of fibrin poured out by the outraged blood-vessels, grow into the deadly false membrane which fills the air-tube and slowly strangles its victim to death. The horrors of a death like that can never fade from the memory of one who has once seen it, and will outweigh the lives of a thousand guinea-pigs. No wonder there was such a widespread and peculiar horror of the disease, as of some ghostly thug or strangler.