The Case of the Unfortunate Baronet: a fragment

A half empty glass stood on the table. Holmes first examined it intensely through his lens, then dipped a single long finger into the pale pink liquid, sniffed it and then tested it with the tip of his tongue. “Talmazide!” he exclaimed.
“Talmazide?”
“Yes Watson, talmazide: the distillation of the sap of a rare South American buttercup, known to the native Indians as xaltopa. A dose of this size is invariably fatal”
“My God, Holmes, Sir Henry must have committed suicide!”
“I think not, Watson. Sir Henry was certainly poisoned, but not by this means. No lips have touched the rim of this glass. Besides, Watson, whoever heard of a suicide who, having prepared a fatal dose, drank only half of it and then put down the glass! We must search elsewhere. This glass is merely an attempt, a very clumsy attempt, to throw us off the scent. Now, Watson, be good enough to recite to me the effects of talmazide poisoning”
“At first, only a slight queasiness”, I said, “Then, increasing lethargy, and after about half an hour, a brief delirium, and finally, if the dose is powerful enough, paralysis of the heart. The chief external sign is discoloration of the eyes.”
“Which is what we find in the unfortunate Sir Henry. So if he was not poisoned by this glass, then when? We know that last night he attended the dinner of an association known as the Silurian Brothers. Now, Watson, I believe that you yourself were once a guest at such a dinner. Tell me what occurred.”
"There were about a dozen gentlemen present. After we had dined, we took it in turns to pledge substantial sums of money to certain charities. I must confess that, although the dinner was magnificent and the charities worthy enough, I did not greatly enjoy the experience. I did not like the atmosphere. I sensed ostentation and vanity in those wealthy enough to pledge large amounts, and moral blackmail upon those, like myself, who could not afford such opulence. I did not wish to attend again.
“But surely, Holmes, you cannot be suggesting that Sir Henry was poisoned at the dinner? He would not have had time to reach home before the fatal dose took effect. And we know from Sir Henry’s manservant that when he arrived in the cab he appeared perfectly healthy.”
Holmes laughed. “Excellent, Watson! My thoughts were running on exactly the same lines. Besides, it is by no means an easy matter to poison a man at a public function. He must have taken the poison some time after the dinner.
“I know of only three men in London who have access to large quantities of talmazide. Come, Watson, it is there that our enquiries must start!”