symptoms, such as giddiness, headache, ringing in the ears, depraved vision, or partial palsy. But it is an error to suppose that warning symptoms always occur; nay, if we may trust the experience of M. Rochoux, they are by no means common: of sixty-three cases which came under his notice nine only had distinct precursory symptoms.[1625] Poisoning with narcotics of course has not any precursory symptom except by fortuitous combination. And consequently, if warning symptoms have occurred, the presumption is, that the cause of death is a natural one.