The first observation of the mobility of the viperine fang and its peculiar structure is ascribed to Felix Fontana,[99] an eminent naturalist and Professor of Philosophy at Pisa, in the eighteenth century. He formed the cabinet of Natural History at Florence, and died 1805, in his 75th year. But the _mobility_ or action of rattlesnake fangs was known long prior to Fontana, and he probably borrowed the expression ‘dog-teeth’ from the old Virginia writers who thus called the fangs. Purchas (1614), quoted in chap. xvi., describes ‘venomous Serpentes, one ten Spannes long, with great Tuskes, which they hide and stretch out at pleasure.’[100] And again, in describing ‘foure kinds of venomous Snakes. The first is greatest, Jararacucu, that is great Jararaca, and they are ten Spannes long: they have great Tuskes hidden in the Mouth along their Gummes, and when they bite they stretch them like a Finger of the Hand; they have their Poyson in their Gummes, their Teeth crooked, and a Stroake vpon them whereby the Poison runneth. Others say they have it within the Tooth which is hollow within. It hath so vehement a Poison that in foure-and-twentie Houres and lesse it killeth a Man.’[101] There can be no doubt but that viperine fangs are here described, those belonging to the South American _Crotalidæ_, under their vernacular but then their only names. Dr. Ed. Tyson, who dissected the first rattlesnake that was handed over to science (p. 275), quite understood the mobility of the fangs, and of the existence of supplementary teeth, though not fully comprehending the nature of these latter; which ‘I could not perceive were fastened to any Bone, but to Muscles or Tendons there. These Fangs were not to be perceived upon first opening the Mouth, they lying couched under a strong Membrane or Sheath, but so as did make a large Riseing there on the Outside of the lesser Teeth of the Maxilla’ (meaning the reserve fangs), ‘but at Pleasure when alive they could raise them to do Execution with, not unlike as a Lyon or a Cat does its Claws.’[102] He found seven reserve fangs on each side; and though they were not, as he tells us, ‘fastened to any bone,’ the illustration represents them growing in regular order according to size in the jaw. In another paper read before the Royal Society in 1726, also anterior to Fontana, on the ‘Fangs of the Rattlesnake,’ the writer, Captain Hall, describes the dissection, which was under the direction of Sir Hans Sloane; and ‘then the Muscles that raise the poisonous Fangs appear.’ This anatomist also found reserve fangs. ‘Putting by this Membrane, the fatal Fangs appear, which on first View seemed only one on each Side, till searching further there appeared four more. The first and largest is fixed in a Bone;’ four others were loose in the membrane.[103]