During the preparation of an exhibition in Pavia dedicated to the centennial anniversary of the death of the Italian Pathologist Paolo Mantegazza, a strange cheratinic horn was found at the Museum for the History of the University of Pavia labelled as ‘spur of a cock transplanted into an ear of a cow.’ After some historical investigation, we found this strange object was at the centre of a scientific correspondence between Mantegazza and Charles Darwin, who made reference to it in his book The Variation of Animals and Plants under Domestication. On 8 May 1929, Italy's fascist regime proudly celebrated the nation's past scientific achievements with a big exhibition in Florence. The University of Pavia contributed several artefacts of historical importance, including one of the first significant examples of interspecies transplantation: a curved horn mounted on a black wooden pedestal with a little accompanying note that read ‘graft of a cockspur in the ear of a calf.’ Six months later, this specimen was sent back to Pavia's newly constituted Museum for the History of the University, where it stood on a shelf – largely unnoticed – for more almost 80 years. Then, in 2010, we were able to reconstruct the fascinating history of this specimen that would link it with the name of Charles Darwin.