paper coincides with more recent investigations in regard to the transmission of diphtheria. I think most of the recent investigations are usually or have been along bacteriological lines rather than along clinical lilies. Since the diphtheria bacillus was discovered, and since the discovery of antitoxin, the mortality from this disease has markedly diminished. Diphtheria mortality averages in most plaees from 5-15%, which is still high. The diphtheria bacillus is said to lose its virulence

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... apart from the body tissues, and, when exposed to sun-light oi< dryness, dies within a few days. The question may then ariso why wo have so many fresh cases of diphtheria when we have these known factors? The reason is that so many carriers are going about. It is known that about 1 to 5% of the community are still diphtheria carriers, many of whom harbor the organism for many'days after the membrane has disappeared from the throat. This is the chief reason why people, going about with the diphtheria bacilli in their nose or throat, are still keeping up the disease. These carriers who are harboring the virulent or non-virulent organisms are the ones who are transmitting the disease. Some investigators believe that true diphtheria bacilli have a power of losing their virulence even after an attack of diphtheria and under favorable conditions for growth may be transformed again to virulent bacilli. The vast number of bacteriologists claim, however, that true diphtheria bacilli arc distinct organisms and that the diphtheroids arc not pathogenic and do not cause true diphtheria. Boards of health in the largest cities no longer fumigate houses where diphtheria has been present, and do'not fumigate for measles or chickonpox, and in some places not for scarlet fever, because of the fact that 'the life of the organisms which cause these diseases is short after leaving the body tissues. We note from the Schick test that there are a number of peoplo known to'have natural immunity to the disease, about 80% of infants, 40-60% of •children, from one to fifteen years of age,'and about 80% of adults. This leaves only a small part of susceptible people, and it ' would seem as though with this knowledge that the mortality from the disease ought to be lower than 10%. The fact remains it has been about the same for the past ten years.