I am very conscious now of these nasty things and what they can do.  Some years ago, our large setter had an infected paw.  Long story short, it had started as a grass seed (one of those long, spiky ones) in his foot – and had travelled almost up to the top of his leg – inside!!!  Our fabulous Vet put him out and managed to find it using a very long pair of tweezers – all done by feel – a marvellous job.  I hate to think what may have happened had it progressed any further.  Rightly or wrongly, we now shave his paws in summer – which, of course, he hates!!