In spite of this admission, however, the sum of the evidence tended strongly to implicate Fletcher, and one or two questions from jurymen suggested a growing belief in his guilt. I had no doubt whatever that if the case had been put to the jury at this stage, a unanimous verdict of “wilful murder” would have been the result. But, as the medical witness returned to his seat, the coroner fixed an inquisitive eye on Thorndyke. “You have not been summoned as a witness, Dr. Thorndyke,” said he, “but I understand that you have made certain investigations in this case. Are you able to throw any fresh light on the circumstances of the death of the deceased, Joseph Riggs?” “Yes,” Thorndyke replied. “I am in a position to give important and material evidence.” Thereupon he was sworn, and the coroner, still watching him curiously, said: “I am informed that you have examined samples of the blood of deceased and the blood which was found in the hall of deceased’s house. Did you examine them, and if so, what was the object of the examination?” “I examined both samples and also samples of the blood of Robert Fletcher. The object was to ascertain whether the blood on the hall floor was the blood of the deceased or of Robert Fletcher.” The coroner glanced at the medical witness, and a faint smile appeared on the face of each. “And did you,” the former asked in a slightly ironical tone, “form any opinion on the subject?” “I ascertained definitely that the blood in the hall was neither that of the deceased nor that of Robert Fletcher.” The coroner’s eyebrows went up, and once more he glanced significantly at the doctor. “But,” he demanded incredulously, “is it possible to distinguish the blood of one person from that of another?” “Usually it is not, but in certain exceptional cases it is. This happened to be an exceptional case.” “In what respect?” “It happened,” Thorndyke replied, “that the person whose blood was found in the hall suffered from the parasitic disease known as filariasis. His blood was infested with swarms of a minute worm named _Filaria nocturna_. I have here,” he continued, taking out of his research-case the two bottles and the three boxes, “thirty-six mounted specimens of this blood, and in every one of them one or more of the parasites is to be seen. I have also thirty-six mounted specimens each of the blood of the deceased and the blood of Robert Fletcher. In not one of these specimens is a single parasite to be found. Moreover, I have examined Robert Fletcher and the body of the deceased, and can testify that no sign of filarial disease was to be discovered in either. Hence it is certain that the blood found in the hall was not the blood of either of these two persons.” The ironic smile had faded from the coroner’s face. He was evidently deeply impressed, and his manner was quite deferential as he asked: “Do these very remarkable observations of yours lead to any further inferences?”