An air raid drill at Seattle College caught students William Bates, left, and Edna Mae Farrell, right, while they were eating their lunch in the school café, but they simply took shelter under the table and continued eating in Seattle, Washington, March 17, 1942. Air raid wardens said 350 students left their classrooms and assembled in shelters within one minute in first at the college. (Photo by AP Photo)

In this Wednesday, April 8, 2020, photo, youths remove their mask to record a dance routine on the streets of Wuhan in central China's Hubei province. Released from their apartments after a 2 1/2-month quarantine, residents of the city where the coronavirus pandemic began are cautiously returning to shopping and strolling in the street but say they still go out little and keep children home while they wait for schools to reopen. (Photo by Ng Han Guan/AP Photo)

Enya Kim from the Natural History department at auctioneers Bonhams & Butterfields stands in front of one of the world's largest set of shark jaws comprised of about 180 fossil teeth from the prehistoric species, Carcharocles megalodon, which grew to the size of a school bus, at the Venetian Resort Hotel Casino September 30, 2009 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

Mortsafes were contraptions designed to protect graves from disturbance. Resurrectionists had supplied the schools of anatomy in Scotland since the early 18th century. This was due to the necessity for medical students to learn anatomy by attending dissections of human subjects, which was frustrated by the very limited allowance of dead bodies – for example the corpses of executed criminals – granted by the government, which controlled the supply.

A group of daredevil divers get perilously close to a school of deadly sharks – and one even lies on his back with his arm folded. The relaxed diver swims on his back and almost hugs the shark who is floating directly above him. The freedivers – Carlos Estrabeau, 28, and 29-year-old Ocean Ramsey – are friends with photographer Raul Boesel Jr. Photographer Raul Boesel Jr from Curitiba, Brazil, travelled to West End in the Bahamas to capture images of the giant sharks. (Photo by Raul Boesel/Solent News & Photo Agency)

Secondary school students perform a barefoot “pilgrimage of suffering” to support the Occupy Central civil disobedience movement at the Admiralty protest site in Hong Kong November 30, 2014. It has been two months since police first fired tear gas to disperse demonstrators from the main protest site in the Admiralty district next to government offices in the heart of the Asian financial centre. (Photo by Bobby Yip/Reuters)