Attribution 4.0 International (CC BY 4.0)
You can use this work for any purpose, including commercial uses, without restriction under copyright law. You should also provide attribution to the original work, source and licence. Read more about this licence.
Credit
M0016616: Illustration of diagramatic section of Hewitt's valved stopcock incorporated in his nitrous oxide apparatus. Attribution 4.0 International (CC BY 4.0). Source: Wellcome Collection.