Enid Porter’s Cambridgeshire Customs and Folklore (1969) relates an interesting tale of the Fen’s Black Viper.
Apparently the Black Viper [common European Adder] was common to the undrained peat Fens of the past and that black reptile, invisible against the dark peaty soil, would rear itself up on the approach of a human being, ready to inflict a bite which could be fatal.
NOTE: Occasionally Adders are seen that are almost totally black in colour (melanistic). Although not very common, in some populations black individuals can be seen quite often. This appears to be a purely genetic trait rather than a consequence of their environment. Supposedly these animals are more venomous, but this is not the case in reality.
George Borrow wrote in 1810 of an ‘old viper hunter and herbalist‘ who he met with the Gypsies at Whittlesea Mere who had ‘a viper that had lain in his chest‘.
We now know of course that the Adder is not an aggressive species but the old Fenmen believed that the black vipers were attracted by the scent of a menstruating woman and so would often make their way into the rough shacks of the Fen Dwellers.
A Fenland tradition says that black vipers fed on snails, which they swallowed hole, the shells passing through their digestive organs and being excreted as a brown powder, known then as Viper’s Gloss. Records suggest that monks would use this substance to polish gold and silver and even as late as the end of the eighteenth century publicans used the gloss on their pewter tankards. The powder, which had an unpleasant odour, which clung to any place in which it was stored, was sent by Fen lighters to Cambridge, where it was used in the colleges for burnishing silver.
The Fenland Witches were reputedly able to tame the vipers and to extract their fangs, which were preserved in home-made wine and used to procure abortions. They would also feed the serpents milk throughout the Summer months before slitting open their bellies to remove the accummulated fat. They would then sew up the snakes with horsehair and place them in a dark cupboard from which they would emerge unharmed the following Spring. This fat was subsequently melted down to make an ointment to treat ulcers and sores.