The doctor bent over this and uttered an exclamation of amazement. Opening the case which he had laid down by his side he took from it a pair of forceps, and applied them to the spot on Mr. Copperdock’s back. From this he withdrew something, which he carried over to the light, and beckoned to Whyland to inspect. “See that?” he said. “That’s the end of a fine hypodermic needle. I’m beginning to see what happened, now. He was injected with some powerful toxic agent by means of a hypodermic syringe, the needle of which broke off in the process. The nature of the poison we shall be able to determine by an examination of this fragment. But I don’t understand that white incrustation. Let me have another look at it.” He selected a small phial from his case, put the fragment of the needle into it, and labelled it. Then he turned once more to Mr. Copperdock’s body, and examined the patch once more with a lens. Finally he removed some of the white powder and put it in another phial, which he also sealed and labelled. Then he beckoned Whyland aside, and the two conversed for a moment in low whispers. “This is really most extraordinary,” said the doctor. “This man undoubtedly died from an injection of poison administered hypodermically. You remember the case of Colburn, the baker, last year?” “Yes, I remember it well,” replied Whyland. “What about it, doctor?” “Well, of course, I can’t say definitely as yet,” replied the doctor guardedly. “But it seems to me that the symptoms in the two cases are remarkably similar. I would go so far as to hazard the opinion that the same poison was employed in both cases. Now, in the present case, you, I take it, are chiefly interested in the agency by which the poison was administered. Well, it is possible that in this case it was self-administered. One can just manage to run a hypodermic needle into oneself below the left shoulder-blade. Here’s a syringe. There’s no needle in it. Hold it in your left hand. That’s right. Now, see if you can press the nozzle against your back in the place corresponding to the spot on Mr. Copperdock’s body.” Whyland obeyed, and after some fumbling contrived to reach the exact spot. “Yes, it can be done, but it’s precious awkward,” he remarked, handing the syringe back. “Exactly,” agreed the doctor. “That may account for the needle having broken off. Mind, I’m only suggesting a possibility, not laying down a theory. That’s your job. Now we come to the white incrustation round the puncture. Unless I’m greatly mistaken, it is potassium carbonate. Should it prove to be so, the fact would be of considerable significance.” “Why?” enquired Whyland. “I’m afraid I don’t quite follow you, doctor.”