For many years it has been known that puerperal sepsis could be carried by the obstetrician from house to house, and it was made a rule that an infected physician or midwife should not practice for six weeks. This stand was taken, in the course of time, by the profession as the result of experience, before there was any real knowledge of the causal relation of bacteria to infection. This rule of the old practitioners, based on long observation, has been proved correct in later days when the real causes of pathologic conditions were more thoroughly understood.
Things have changed in the last thirty years, since we have been able to demonstrate the bacterial origin of many diseases, and especially since Lister called attention to the cause of surgical failures. We still have septic infections of various kinds, however, and every possible precaution is taken to avoid them. We have