“’I made a post-mortem examination of the body and found that death was due to poisoning by strophanthin, which appeared to have been injected into the thigh.  The two tubes which I found on the dressing-table would each have contained, if full, twenty tabloids, each tabloid representing one five-hundredth of a grain of strophanthin.  Assuming that the whole of this quantity was injected the amount taken would be forty five-hundredths, or about one twelfth of a grain.  The ordinary medicinal dose of strophanthin is one five-hundredth of a grain.

“’I also found in the body appreciable traces of morphine—­the principal alkaloid of opium—­from which I infer that the deceased was a confirmed opium-smoker.  This inference was supported by the general condition of the body, which was ill-nourished and emaciated and presented all the appearances usually met with in the bodies of persons addicted to the habitual use of opium.’

“That is the evidence of the surgeon.  He was recalled later, as we shall see, but, meanwhile, I think you will agree with me that the facts testified to by him fully account, not only for the change in Jeffrey’s habits—­his solitary and secretive mode of life—­but also for the alteration in his handwriting.”

“Yes,” agreed Thorndyke, “that seems to be so.  By the way, what did the change in the handwriting amount to?”

“Very little,” replied Marchmont.  “It was hardly perceptible.  Just a slight loss of firmness and distinctness; such a trifling change as you would expect to find in the handwriting of a man who had taken to drink or drugs, or anything that might impair the steadiness of his hand.  I should not have noticed it, myself, but, of course, the people at the bank are experts, constantly scrutinizing signatures and scrutinizing them with a very critical eye.”

“Is there any other evidence that bears on the case?” Thorndyke asked.

Marchmont turned over the bundle of papers and smiled grimly.

“My dear Thorndyke,” he said, “none of this evidence has the slightest bearing on the case.  It is all perfectly irrelevant as far as the will is concerned.  But I know your little peculiarities and I am indulging you, as you see, to the top of your bent.  The next evidence is that of the chief porter, a very worthy and intelligent man named Walker.  This is what he says, after the usual preliminaries.

“’I have viewed the body which forms the subject of this inquiry.  It is that of Mr. Jeffrey Blackmore, the tenant of a set of chambers on the second floor of number thirty-one, New Inn.  I have known the deceased nearly six months, and during that time have seen and conversed with him frequently.  He took the chambers on the second of last October and came into residence at once.  Tenants at New Inn have to furnish two references.  The references that the deceased gave were his bankers and his brother, Mr. John Blackmore.  I may say that the deceased