"Not a soul," he answered, working his arms and shoulders as if to get rid of some heavy weight that oppressed his chest.
"Then what has happened that makes you use the oxygen?" I repeated, determined to get some kind of answer from him.
He turned to Leslie. "It was no ordinary asphyxiation, Doctor," he said quickly.
Leslie nodded. "I could see that," he admitted.
"We have to deal in this case," continued Kennedy, his will-power overcoming his weakness, "with a poison which is apparently among the most subtle known. A particle of matter so minute as to be hardly distinguishable by the naked eye, on the point of a lancet or needle, a prick of the skin not anything like that wound of Mendoza's, were necessary. But, fortunately, more of the poison was used, making it just that much easier to trace, though for the time the wound, which might itself easily have been fatal, threw us off the scent. But given these things, not all the power in the world—unless one was fully prepared—could save the life of the person in whose flesh the wound was made."
Craig paused a moment, and we listened breathlessly.
"This poison, I find, acts on the so-called endplates of the muscles and nerves. It produces complete paralysis, but not loss of consciousness, sensation, circulation, or respiration until the end approaches. It seems to be one of the most powerful agents of which I have ever heard. When introduced in even a minute quantity it produces death finally by asphyxiation—by paralyzing the muscles of respiration. This asphyxia is what puzzled you, Leslie."
He reached over and took a white mouse from the huge box on the corner of the table.
"Let me show you what I have found," he said. "I am now going to inject a little of the blood serum of the murdered man into this white mouse."
He took a needle and injected some of a liquid which he had isolated. The mouse did not even wince, so lightly did he touch it. But as we watched, its life seemed gently to ebb away, without pain, without struggle. Its breath simply seemed to stop.