Holmes, Watson, and Miss Morstan have been told that the treasure is enormously valuable. Dr. Watson writes:
"Holmes declares that he overheard me caution him against the great danger of taking more than two drops of castor-oil, while I recommended strychnine in large doses as a sedative."
Obviously intended as humor. But strychnine is one of the most horrible poisons of all, because death comes slowly by inability to breathe, and great suffering.

From the Internet:
The onset of symptoms may occur with a
prodromal syndrome that includes: tonic
twitching of the face and neck muscles,
muscular cramps in the legs, preceded by
restlessness, apprehension, and heightened
acuity of perception (hearing, vision,
feeling) and hyperreflexia. However, the
initial symptoms may be only generalized
violent convulsions. These convulsions can
begin suddenly after any minor sensory
stimulus and last from 50 seconds to 2
minutes. Initially, the convulsions are
clonic but are soon followed by tonic
contractions similar to convulsions due to
tetanus.

The patient remains conscious and has intense
pain. After the convulsions, all the muscles
relax and sometimes the patient falls asleep
from exhaustion. Hyperexcitability recurs
suddenly after 10 to 15 minutes.


Repeated convulsions (1 to 10) are common
before recovery or death. In severe
untreated poisoning, each convulsion lasts
longer than the previous one, and the
intervals between them are shorter.

In reply to:

---

the convulsions are
clonic but are soon followed by tonic
contractions similar to convulsions due to
tetanus.

---

What are these 'tonic' and 'clonic' convulsions characterized by?

And what is that poison that can be found in the bark of the black cherry tree, I believe, that was used by that poisoner, Jim James or Jones years ago in that colony in which so many people poisonsed themselves?

Tonic refers to a steady state of contraction.
Clonic means rapidly alternating contraction and relaxation, as seen in epileptic seizures.

So, are birth contractions tonic?

So, are birth contractions tonic?

Yes, lasting a minute or so, but then recurring...

There can also be a terrible grin/grimace that remains on the face of a victim of strychinine poisoning, sometimes characterized as an "involuntary rictus". (Maybe that's what was in the "Devil's-Foot Root"?)

And what is that poison that can be found in the bark of the black cherry tree, I believe, that was used by that poisoner, Jim James or Jones years ago in that colony in which so many people poisonsed themselves?

from http://www.cultsoncampus.com/jimjones2.html :
"... 913 Peoples Temple members...either drank or were forced to drink a cyanide spiked fruit punch Nov. 18, 1978, at the demand of Jim Jones, a religious leader who took his followers from the San Francisco area to Guyana... "

Another bit of irony:
risus sardonicus ['riːsəs sɑː'dɒnıkəs]
noun
(Pathol) fixed contraction of the facial muscles resulting in a peculiar distorted grin, caused esp. by tetanus
Also called: trismus cynicus
['trızməs 'sınıkəs]
[ETYMOLOGY: 17th Century: New Latin, literally: sardonic laugh]

I think it is also seen in death from tetanus.

Yessirree, wwh, that grin has been mentioned in many a thriller!

And thanks, wof', for looking up Jim Jones and his cult. Hard to believe that it all happened way back in '78. I would have guessed as far back as '80 perhaps, but not back into the '70's. So it's cyanide. Yes. That does ring the right bell.