Leslie and I looked at each other and shook our heads.

“Perhaps I was not wise in giving myself so large an injection on a day when I was overheated and below par otherwise, because of the strain I have been under in handling this case, as well as other work.  However that may be, the added centigram produced so much more on top of the five centigrams I had previously taken that for a time I had reason to fear that that additional centigram was just the amount needed to bring my experiments to a permanent close.

“Within three minutes of the time of injection the dizziness and vertigo had become so great as to make walking seem impossible.  In another minute the lassitude rapidly crept over me, and the serious disturbance of my breathing made it apparent to me that walking, waving my arms, anything, was imperative.  My lungs felt glued up, and the muscles of my chest refused to work.  Everything swam before my eyes, and I was soon reduced to walking up and down the laboratory floor with halting steps, only preventing falling on the floor by holding fast to the edge of the table.

“I thought of the tank of oxygen, and managed to crawl over and turn it on.  I gulped at it.  It seemed to me that I spent hours gasping for breath.  It reminded me of what I once experienced in the Cave of the Winds of Niagara, where water is more abundant in the atmosphere than air.  Yet my watch afterward indicated only about twenty minutes of extreme distress.  But that twenty minutes is one period I shall never forget.  I advise you, Leslie, if you are ever so foolish as to try the experiment, to remain below the five-centigram limit.”

“Believe me, I’d rather lose my job,” returned Leslie.

“How much of the stuff was administered to Mendoza,” went on Kennedy, “I cannot say.  But it must have been a good deal more than I took.  Six centigrams which I recovered from these small samples are only nine-tenths of a grain.  You see what effect that much had.  I trust that answers your question?”

Dr. Leslie was too overwhelmed to reply.

“What is this deadly poison that was used on Mendoza?” I managed to ask.

“You have been fortunate enough to obtain a sample of it from the Museum of Natural History,” returned Craig.  “It comes in a little gourd, or often a calabash.  This is in a gourd.  It is a blackish, brittle stuff, incrusting the sides of the gourd just as if it was poured in in the liquid state and left to dry.  Indeed, that is just what has been done by those who manufacture it after a lengthy and somewhat secret process.”

He placed the gourd on the edge of the table, where we could see it closely.  I was almost afraid even to look at it.

“The famous traveller, Sir Robert Schomburgk, first brought it into Europe, and Darwin has described it.  It is now an article of commerce, and is to be found in the United States Pharmacoepia as a medicine, though, of course, it is used in only very minute quantities, as a heart stimulant.”