HIGH-FLYING TOILET If ever people build cities in space, they will have to deal with the human waste problem. The biggest challenge is weightlessness; without gravity a conventional toilet would allow human waste to escape into the air... NASA
HI-TECH TOILET Toilets are still evolving. The Japanese company Toto introduced the Washlet in 1980, which uses a bidetlike warm water spray to automatically clean the anal/urethral area instead of relying on toilet paper, the latter of which can result in hand and finger contamination by disease-causing germs... TOTO Global Group
VICTORIAN CONVENIENCE As cities grew much larger in the late 19th century, precursors of the modern flush toilet became more popular. Innovations such as the water trap (which kept sewer odors from rising into the home) and the U-bend (which decreased the number of blockages) helped to increase the flush toilet's appeal... National Library of Medicine
DIRTY WORK Without functioning sewer systems, the buildup of waste from latrines requires either that they be cleaned out or regularly moved. Here a "frogman" cleans out a latrine pit in Dar es Salaam, Tanzania... Rémi Kaupp
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BALANCING ACT Even basic-looking latrines can be hygienic if they are carefully sited and properly maintained. The National Library of Medicine
WATCH OUT BELOW By the Middle Ages, sanitary engineering in Europe was still relatively primitive. These garderobes funneled human waste outside the walls of Hadleigh Castle in England. William/www.geograph.org.uk
ANTIQUE LATRINE Roman engineers understood some of the important aspects of basic sanitation, including efforts to keep human excrement away from sources of drinking water. This latrine, in Ostia Antica, fed directly into a sewer... Jan Theo Bakker/Internet Group Ostia
WHEN YA GOTTA GO For millennia humans have relieved themselves anywhere they could—a practice public health experts call "open defecation." Bernard Picart: Le Parfumeur
![A Brief History of the Toilet [Slide Show]](https://static.scientificamerican.com/sciam/cache/file/D65C4F3B-E4EF-47BD-AAFB76DE11B2EB4D.jpg?w=590&h=393)
