I believe that one can determine the age of a fox from a sectional analysis of its teeth, in much the same way that dendrochronology works. I therefore removed part of a lower jaw from one I shot last night as the first step in doing just this. Robert Bucknell wrote in 'Going Foxing' that you should 'soften the tooth in acid', but he didn't say what kind of acid, or for how long one should immerse the said dental appendage. I would therefore be most grateful for any advice anyone here can give me in helping me move on up the ladder of vulpine anatomical knowledge...