Life and health

Cotton wool spots

Cotton wool spots (CWS) are fluffy yellow-white retinal lesions of accumulated axoplasmic debris in the nerve fiber layer, signaling ischemia from diabetes, hypertension, HIV, vein occlusion, or emboli; usually resolving in 6-12 weeks.

Cottonseed oil

Cottonseed oil: cooking oil from cotton seeds, a ginning byproduct requiring refining to remove toxic gossypol. Fatty acid profile 70% unsaturated; once dominant U.S. food fat, now 2–3% of global vegetable oil.

Cottontail rabbit

Cottontail rabbit, genus Sylvilagus; North American lagomorph named for its white cotton-ball tail. Eastern cottontail (S. floridanus) ranges across the eastern US to Central America, breeds prolifically, and was never domesticated.

Cotula

Cotula (button daisies, brassbuttons) is a genus of about 51 Asteraceae herbs in tribe Anthemideae, native from Africa to Australasia, with small disciform button-like flower heads; distinct from Anthemis cotula, stinking chamomile.

Cotula coronopifolia

Cotula coronopifolia (brass buttons, buttonweed) is a southern African Asteraceae wetland herb, invasive in Europe, North America, and Australasia; it is halotolerant, spreads via waterbird gut passage, and was first recorded wild in Britain in 1869.

Cotyledon

Cotyledon: the seed leaf of a plant embryo; one in monocots, two in dicots. Stores food for the embryo, may photosynthesize above ground (epigeal) or stay below (hypogeal), and underpins the John Ray 1682 classification of flowering plants.

Cotylorhiza tuberculata

Cotylorhiza tuberculata (Macri, 1778), the fried egg jellyfish, is a Mediterranean-endemic rhizostome scyphozoan with zooxanthellae symbionts, annual late-summer blooms, a harmless sting, and collagen and bioindicator uses.

Oct 20, 2026

Coua

Coua is a genus of ten cuckoo species (family Cuculidae) endemic to Madagascar, named from the Malagasy koa. Mostly terrestrial, insectivorous dry-forest birds; Coua delalandei is extinct and Giant Coua was listed Vulnerable in 2025.

Couch's spadefoot toad

Couch's spadefoot toad (Scaphiopus couchii, Couch's spadefoot) is a burrowing desert frog of the southwestern US and Mexico, breeding explosively in temporary rain pools with tadpoles metamorphosing in as little as 8 days.

Couching (ophthalmology)

Couching is an ancient, now obsolete cataract operation in which a needle dislodges the clouded lens from the visual axis, leaving it inside the eye; it persists in parts of West Africa and Asia.

Cougar

Cougar (Puma concolor), also called puma, mountain lion, or panther: a large solitary felid ranging from northern Canada to South America, preying mainly on deer, with densities of 1–7 per 100 km² and frequent livestock-conflict management in western North America.

Cough

Cough: a protective airway-clearing reflex triggered by receptors in the throat, larynx, and bronchi. Acute cough lasts under 2-3 weeks; chronic cough over 8 weeks. Causes, nerve pathways, and treatment evidence.

Cough detection

Cough detection is the automated identification of cough events in audio or sensor recordings, turning cough into an objective count; systems like the Leicester Cough Monitor and VitaloJAK support 24-hour monitoring.

Cough variant asthma

Cough variant asthma (CVA) is an asthma subset with cough as the sole or main symptom, without wheeze or dyspnea. It causes 25-42% of chronic cough, features bronchial hyper-responsiveness and eosinophilic inflammation, and progresses to classic asthma in 30-40% of untreated adults.

Couma

Couma is a genus of five species of latex-yielding trees in the dogbane family, native to Central and South America and harvested in the Amazon for its sweet latex, sorva.

Coumachlor

Coumachlor (CAS 81-82-3, p-chlorowarfarin, Tomorin) is a first-generation hydroxycoumarin anticoagulant rodenticide and warfarin analog, a vitamin K antagonist, historically used in Canada, France, Germany, and Malaya and now largely unregistered.

Coumafuryl

Coumafuryl (fumarin, tomarin, Ratafin), CAS 117-52-2, is an obsolete first-generation 4-hydroxycoumarin anticoagulant rodenticide introduced around 1952, acting as a vitamin K antagonist; not approved in the EU.

Coumaphos

Coumaphos (Co-Ral, Asuntol) is an organophosphorus insecticide and acaricide, C14H16ClO5PS, controlling ticks, lice, and fleas on livestock via acetylcholinesterase inhibition; used in USDA fever tick dip vats and formerly in Australia.

Coumatetralyl

Coumatetralyl (Racumin) is a first-generation 4-hydroxycoumarin anticoagulant rodenticide introduced by Bayer in 1957, a vitamin K antagonist approved in the EU for PT14 rodent control but with no US EPA-registered products.

Counterconditioning

Counterconditioning is a behavior therapy procedure that replaces an unwanted conditioned response to a stimulus with a new, incompatible response, such as relaxation or reward.

Counterimmunoelectrophoresis

Counterimmunoelectrophoresis (CIE), also called counter-current immunoelectrophoresis, is a serological technique in which an electric field drives antigen and antibody together in a gel, forming a visible precipitin line.

Counterpulsation

Counterpulsation is a form of mechanical circulatory support that inflates a balloon or leg cuffs during diastole to raise coronary perfusion and reduce left ventricular work.

County and regional bryophyte floras of the British Isles

County and regional bryophyte floras of the British Isles: published accounts of mosses, liverworts and hornworts by Watsonian vice-county, from 19th-century single-author floras to modern tetrad atlases under the British Bryological Society's Census Catalogue system.

County Hospitals

County hospitals are hospitals owned and operated by county governments, historically the US care providers of last resort for indigent patients; key facts cover governance, safety-net funding, quality, and closures.

Coup contrecoup injury

Coup contrecoup injury: paired focal brain contusions at and opposite the site of a head blow, caused by brain-skull contact during rapid acceleration or deceleration; mechanisms include pressure gradients, cavitation, and rotation, distinguishing it from diffuse axonal injury.