An undated archive picture shows a dog pulling a Belgian machine gun at an unknown location in northern France. A Viscount in the Armoured Cavalry Branch of the French Army left behind a collection of hundreds of glass plates taken during World War One (WWI) that have never before been published. The images, by an unknown photographer, show the daily life of soldiers in the trenches, destruction of towns and military leaders. The year 2014 marks the 100th anniversary of the start of WWI. (Photo by Collection Odette Carrez/Reuters)

The Lamb National takes place for the racegoers at Ascot Racecourse on April 2, 2017 in Ascot, England. (Photo by Alan Crowhurst/Getty Images)

The tempestuous stellar nursery called the Carina Nebula, located 7,500 light-years away from Earth in the southern constellation Carina. (Photo by Reuters/NASA)

Brain-on-a-chip. Dazzling in green and magenta this image shows the nerve fibres (in green) produced by neural stem cells (in magenta) as they grow on a synthetic gel. Captured by a technique known as confocal microscopy, the image is part of research shedding light on how tinkering with the environment can affect the way in which nerve fibres grow. (Photo by Collin Edington and Iris Lee/Massachusetts Institute of Technology/Wellcome Images)

Revelers march during the Greenwich Village Halloween Parade, Tuesday, October 31, 2017, in New York. (Photo by Andres Kudacki/AP Photo)

Beluga the bog poses as Britney Spears during the 17th annual Tompkins Square Halloween Dog Parade October 28, 2007 in New York City. The event is the largest dog Halloween party in the United States with an annual attendance of over 400 costumed dogs. (Photo by Mario Tama/Getty Images)

A participant in costume poses to a camera after a Halloween parade in Kawasaki, south of Tokyo, Japan October 30, 2016. More than 130,000 spectators turned up to watch the parade, where about 2,600 participants dressed up in costumes, according to the organiser. ((Photo by Kim Kyung-Hoon/Reuters)

The 2016 Greenwich Village Halloween parade, October 31, 2016 in the Manhattan borough of New York City. (Photo by Anthony Causi)