Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

A 2-year-old Florida panther is released into the wild by the Florida Fish and Wildlife Conservation Commission (FWC) on April 3, 2013 in West Palm Beach, Florida. The panther and its sister had been raised at the White Oak Conservation Center since they were 5 months old. The FWC rescued the two panthers as kittens in September 2011 in northern Collier County after their mother was found dead. The panther is healthy and has grown to a size that should prepare him for life in the wild. (Photo by Joe Raedle)

A zoo keeper feeds Diego, a three month old howler monkey, which is reared at Edinburgh Zoo, July 29, 2008 in Scotland. (Photo by Jeff J. Mitchell/Getty Images)

An artist's impression of a growing supermassive black hole located in the early Universe is seen in this NASA handout illustration released on June 15, 2011. Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-Ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies. (Photo by Reuters/NASA/Chandra X-Ray Observatory/A.Hobart)

Black Nazarene devotees clamber on top of one another to to touch the cross on January 9, 2015 in Manila, Philippines. The Feast of the Black Nazarene culminates in a day long procession on January 9 as barefoot devotees march to see and touch the image of the Black Nazarene. The Black Nazarene is a dark wood sculpture of Jesus brought to the Philippines in 1606 from Spain and considered miraculous by Filipino devotees. The event falls a week ahead of the visit of Pope Francis who will travel to Leyte and Manila during his visit to the Philippines from January 15–19. The visit is expected to attract crowds in the millions as Filipino Catholics flock to catch a glimpse of the leader of the Catholic Church. The Philippines is the only Catholic majority nation in Asia with around 90 percent of the population professing the faith. (Photo by Dondi Tawatao/Getty Images)

A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)

Riot police walk in the street as a couple kiss on June 15, 2011 in Vancouver, Canada. Vancouver broke out in riots after their hockey team the Vancouver Canucks lost in Game Seven of the Stanley Cup Finals. (Photo by Rich Lam/Getty Images)