Introduced by the obstetrician and profesor of midwifery, Sir James Simpson (1811-1870), sea-tangle uterine tents (laminaria digitalia) were used for dilating the os and cervix uteri to facilitate birth. Laminaria, a marine plant, was suggested by Simpson as a substitute for sponge tents for this purpose. Being smaller but more rigid, it could be more easily introduced into small openings and canals than sponge tents. Laminaria can swell by up to four times its original diameter by absorbing fluid, thereby increasing dilation. Simpson was also the first to use ether to aid pain relief in obstetric practice in the UK on 19 January 1847, and subsequently introduced chloroform on 8 November 1847.
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