For the last year I have taken my morning walk in the Cemetery of Montparnasse. Right from the start, whenever there was moisture in the air, I noticed on returning home an unpleasant taste of verdigris in my mouth, which remained with me during the morning for at least a couple of hours. As the taste of verdigris did not appear when I forwent my walk in the cemetery, I concluded that it had been occasioned by the miasmas of the dead. And when mild toxic symptoms resembling those of a cupric salt also appeared, I began to wonder if it really was copper. One morning I therefore took along a bottle of ammonia, expecting to obtain a shade of blue which is, of course, characteristic where solutions of cupric salts are concerned, but it did not materialise. I had with me some lead acetate and within half an hour I obtained a small amount of black lead sulphide and a little carbonate. An old textbook on poison had recently come my way, in which I had read about Raspail's epoch-making appearance in a celebrated trial for murder by poison, where he warned against placing too great a confidence in chemical analyses, when the unexplained capacity of the reactive agent to participate in the new formation of the element that is being sought may often lead to a synthesis. In the course of the discussion there was also a report about the occurrence of copper in the human body when it has not been introduced by chance or with criminal intent.