Doctor Nott produced it in a covered basket.
Quickly Kennedy drew off a little of the blood of the cat and held it up to the light along with the human samples. The difference was apparent.
“You see,” he explained, “carbon monoxide combines firmly with the blood, destroying the red colouring matter of the red corpuscles. No, Doctor, I'm afraid it wasn't carbonic oxide that killed the lovers, although it certainly killed the cat.”
Doctor Nott was crestfallen, but still unconvinced. “If my whole medical reputation were at stake,” he repeated, “I should still be compelled to swear to asphyxia. I've seen it too often, to make a mistake. Carbonic oxide or not, Templeton and Miss Wainwright were asphyxiated.”
It was now Whitney's chance to air his theory.
“I have always inclined toward the cyanide-of-potassium theory, either that it was administered in a drink or perhaps injected by a needle,” he said. “One of the chemists has reported that there was a possibility of slight traces of cyanide in the mouths.”
“If it had been cyanide,” replied Craig, looking reflectively at the two jars before him on the table, “these blood specimens would be blue in colour and clotted. But they are not. Then, too, there is a substance in the saliva which is used in the process of digestion. It gives a reaction which might very easily be mistaken for a slight trace of cyanide. I think that explains what the chemist discovered; no more, no less. The cyanide theory does not fit.”
“One chemist hinted at nux vomica,” volunteered the coroner. “He said it wasn't nux vomica, but that the blood test showed something very much like it. Oh, we've looked for morphine chloroform, ether, all the ordinary poisons, besides some of the little known alkaloids. Believe me, Professor Kennedy, it was asphyxia.”
I could tell by the look that crossed Kennedy's face that at last a ray of light had pierced the darkness. “Have you any spirits of turpentine in the office?” he asked.
The coroner shook his head and took a step toward the telephone as if to call the drug-store in town.