Dark absorption features in the solar spectrum, mapped and labelled by Joseph von Fraunhofer. They give reproducible wavelength landmarks for spectroscopy and optical measurements. Solar and terrestrial absorbers contribute different features to a ground-observed solar spectrum.

The historical hypothesis that familiar living organisms arise directly from nonliving preparations. Experiments controlling contamination challenged this account: preventing access by organisms while retaining exposure to air tests whether growth requires a biological source. This does not experimentally rule out ancient abiogenesis.

An RNA virus that causes poliomyelitis. Many infections do not become paralytic disease, separating acquisition of the virus from one severe clinical outcome.

Toxic injury caused by strychnine, which removes inhibitory control of spinal motor activity. Stimulus-sensitive painful muscle contractions can occur while consciousness is initially retained, making the mechanism different from an ordinary loss-of-consciousness seizure.^[ref]

Toxic injury from carbon monoxide, which interferes with oxygen delivery and cellular function. Formation of carboxyhaemoglobin is central, but measured blood levels depend on elapsed time and oxygen exposure as well as the original exposure.^[ref]

Toxic injury in which cyanide impairs cellular oxygen use, including through inhibition of cytochrome c oxidase. Oxygen can be available in blood while tissues fail to use it effectively, distinguishing the mechanism from simple lack of inspired oxygen.^[ref]

A substance capable of causing harmful biological effects under a particular exposure. Poisoning depends on amount, chemical form, route and timing; a substance’s mere presence does not specify either a toxic dose or a causal explanation of illness.

A highly toxic alkaloid that interferes with inhibitory neurotransmission, producing stimulus-sensitive muscle spasms in strychnine poisoning. Its biological effect connects blockade of inhibitory signaling with excessive motor activity.^[ref]

Analytical investigation of potentially harmful substances and their products in biological or environmental samples. Identification and quantity answer different questions, and both require attention to contamination, chemical specificity and the time between exposure and sampling.

Toxic effects of opioids, especially respiratory depression; severe poisoning can require artificial respiration and naloxone.

Toxic effects of antimony compounds, which depend on chemical form and exposure. Gastrointestinal and systemic injury can occur; a positive analytical test must be interpreted alongside the identified compound and exposure history.

A medical procedure that introduces and withdraws fluid through a gastric tube to remove stomach contents. Its possible benefit depends on the exposure and timing, while aspiration and mechanical injury are important limitations; it is not a routine response to every ingestion.

The acute toxic syndrome caused especially by white phosphorus, distinguished from ordinary dietary phosphate.

Harmful elevation of inspired carbon dioxide, producing carbon dioxide retention and disturbed acid–base balance. It differs from simple displacement of oxygen: high carbon dioxide can have direct physiological effects even when oxygen is present.

Toxic injury caused by lead exposure. Lead can disturb nervous-system development and blood formation; the amount measured in blood and the cumulative amount stored in the body describe related but different aspects of exposure.

Acute impairment caused by ethanol, affecting behavior, coordination and nervous-system function. At greater exposure, depressed consciousness and breathing can occur; observed impairment depends on more than beverage concentration alone.

Poisoning involving muscarinic receptor blockade, with manifestations including delirium, dryness and mydriasis.^[ref]

Toxic effects of oxalic acid, including local corrosive injury, disturbed calcium balance and possible acute kidney injury with calcium oxalate deposition.^[ref][ref]

A scientist who investigates toxic exposures and their biological effects. A toxicologist may connect analytical detection of a substance with dose, mechanism and observed injury, distinguishing the presence of a chemical from evidence that it caused harm.

An agent used to counteract a particular poison or its effects. For example, naloxone counteracts opioid-mediated depression of breathing through receptor antagonism; an antidote’s mechanism is specific rather than a universal neutralization of every toxic exposure.