M. Latour seemed nervous and ill at ease.  He shifted from side to side as if M. Godin’s glance had pierced him like a rapier, and he were trying vainly to wriggle off of it.  He seemed unable to disengage himself and at length replied in a wearied and spiritless tone: 

A. In two particulars only.  In the first place, it was very small, having a capacity of but five or six drops, and, in the second place, it was provided with an internal spring which, when released, worked the plunger and ejected the contents with extreme rapidity.

Q. What operated this spring?

A. Around the needle-like point of the syringe, less than a quarter of an inch from its end, was a tiny, annular bit of metal.  This little metallic collar was forced upward by the pressure of the flesh as the sharp point entered it, and this movement released the spring and instantly and forcibly ejected the contents of the cylinder.

Q. Did you use a poison in this syringe?

A. Yes, sir.

Q. What did you use?

M. Latour hesitated and shifted helplessly about as if he dreaded to go farther into these particulars, and fondly hoped someone might come to his rescue.  His gaze seemed to shift about the room without in the least being able to disentangle itself from that of M. Godin.  He remained silent and the question was repeated.

Q. What did you use?

Again the witness hesitated while everyone, save only Maitland and Godin, leaned eagerly forward to catch his reply.  At length it came in a voice scarcely above a whisper.

A. Anhydrous hydrocyanic acid.

A long-drawn “Hum!” escaped from Maitland, while M. Godin gave not the slightest indication of surprise.  It was quite evident to us all that the astute Frenchman had acquired complete control of the case before he had arrested the assassin.  At this juncture the Court said, addressing Maitland: 

“This substance is extremely poisonous, I take it.”

“Your Honour,” Maitland replied, “it is the most fatal of all poisons known to chemists.  It is also called cyanhydric, and, more commonly, prussic acid.  An insignificant amount, when inhaled or brought into contact with the skin, causes immediate death.  If a drop be placed upon the end of a glass rod and brought toward the nose of a live rabbit he will be dead before it reaches him.”

A profound silence—­the death-like quiet which accompanies an almost breaking tension—­reigned in the court-room as Maitland turned again to Latour.

Q. I understand you to say you used anhydrous hydrocyanic or cyanhydric acid.

A. Yes, sir.

Q. Do you sufficiently understand chemistry to use these terms with accuracy?  Might you not have used potassium cyanide or prussiate of potash?

A. I am a tolerably good chemist, and have spoken understandingly.  Potassium cyanide, KCN, is a white, crystalline compound, and could hardly be used in a hypodermic syringe save in solution, in which condition it would not have been sufficiently poisonous to have served my purpose.