“She went--and once again I had to go through all the bother of advertising. The wretched thing now began to haunt more vigorously than ever. It attacked Emily, the cook, on the kitchen staircase, and Mark, my general factotum, in the stables, both leaving in consequence, and both being afterwards taken very ill. Indeed it was the report of their illness that prompted me to wage war against the ghost--if I had to leave the house, it should not be till I had ascertained something more definite about my enemy. I would try and discover its identity--what it actually was! With this end in view I laid every trap imaginable, my ingenuity being at length rewarded by finding a faint and barely perceptible impression on the surface of a very large tray full of a carefully prepared mixture of gelatine and wax. I had placed the tray in one of the passages usually frequented by the EVIL PRESENCE. On examining the impression under a powerful microscope I fancied I could detect innumerable granules composed of radiating threads with bulbous terminations. “Elated at my success and wondering very much what it represented, I took a photograph of the impression and sent it to a medical friend--a bacteriologist--in London, whom I knew to be interested in psychical research. In the course of a few days he came to see me, and, pointing to the wax tablet, remarked: “‘I showed the photograph you sent me to some of my colleagues, and we came to the conclusion that the impression bore a distinct likeness to a number of actinomyces, which, as you may know, are a kind of fungi inimically disposed to every kind of animal--cattle in particular. Indeed they are in the main responsible for one of the most common and deadly bovine diseases which is called actinomycosis, and is acquired by cattle eating infected barley or other cereal, the actinomyces adhering to the tongue or jaw. “‘In man the disease is very similar in its clinical character and may be caused by a number of organisms belonging to the streptothrix group (I fear this is rather too technical for you) forming colonies in the tissues and obtaining access to the body from a carious tooth or not infrequently from the tonsil. “‘The disease is sometimes wrongfully diagnosed as tuberculosis; it usually occurs in farmers, millers, and others who are brought in contact with grain; it has a tendency to spread locally, and although not dangerous in itself, may become so by attacking important organs or by becoming generalised, thereby giving rise to pyæmic abscesses in all parts of the body.