= Solution
\b[Poisoning by <belladonna> characteristically combines delirium with dry secretions and dilated <pupils>; poisoning by hydrocyanic acid can cause very rapid collapse with failure of <breathing>.] The two patterns are distinctive descriptions, not infallible diagnoses from one symptom.
With <belladonna>, expect dryness of the mouth and throat, difficulty swallowing, blurred vision and <mydriasis>. The skin may become hot, dry and flushed; the <pulse> is often rapid. Restlessness, confusion, visual <hallucinations> and agitated <delirium> may be prominent: the person may talk incoherently or pick at imaginary objects. Reduced intestinal activity and <urinary retention> can accompany the dryness. Severe poisoning can proceed to <seizures>, depressed <consciousness>, <coma> and circulatory failure. This is now understood chiefly as an <antimuscarinic poisoning> syndrome produced by alkaloids including <atropine>, which oppose the action of <acetylcholine> at <muscarinic receptors>.<Anticholinergic Syndrome by the Royal Children’s Hospital Melbourne>[Background; characteristic central and peripheral signs; severity table]{ref}
Hydrocyanic acid is <hydrogen cyanide>, historically also called prussic acid. Depending on the route and amount, early complaints may include dizziness, <headache>, anxiety, <nausea>, weakness and a sense of suffocation. Rapid <breathing> may give way to slow or failing <breathing>, followed by <seizures>, <coma>, circulatory collapse and death. A sufficiently large exposure may be so rapid that an elaborate sequence of preliminary symptoms is not observed. There is no single obligatory interval from exposure to collapse.<Cyanide chemical fact sheet by CDC>[How cyanide works; signs and symptoms; severity and route of exposure]{ref}
In modern terms, <cyanide> impairs cellular use of <oxygen>, including inhibition of <cytochrome c oxidase> in <cellular respiration>. An apparently oxygenated colour therefore cannot exclude serious poisoning. A bitter-almond odour is an unreliable clue: it may be absent or not perceived, and no examiner should intentionally smell a suspect sample. The historical term “narcotic poison” does not mean that either <belladonna> or <hydrogen cyanide> acts like an <opioid>. The receptor and cellular explanations above are present scientific interpretations, rather than molecular explanations available in 1864.<Hydrogen cyanide emergency response information by NIOSH>[Signs/symptoms and chemical identification: odour is an inadequate warning]{ref}
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