In the course of my investigations I entered a wash-house belonging to one group of the houses in question. I was followed in by its owner, an old lady, who sought at once to satisfy my curiosity by assuring me that the building was rarely used; indeed, that the last time it was used was six weeks ago, at which date she had washed some linen there for a young man who had been very ill, and who lived some distance away. I had before this noticed that all the cottages were provided with sinks in their living-rooms, and that by means of these sink-pipes, which were in unbroken communication with a drain outside, offensive effluvia at times made their way into the dwellings, these having been especially noticed toward evening, when the houses were shut up and the fires were lighted. It at once occurred to me that if the sick man referred to had suffered from enteric fever, and if the drains for the several parts of the square all communicated
Fig. 2.
with the sewer by which the liquid refuse from the wash-house was conveyed away, then a specifically contaminated sewer-air had replaced the ordinary foul effluvia, and that in this way infection had been "laid on" to the several households. I found that the young man
