Common Inkcap Coprinopsis atramentarius
!!! Edible only in rare circumstances!!!
Note: this is an expansion on the text in the book about this species within the chapter on the Shaggy Inkcap.
The Common Inkcap, which, annoyingly, is much less common than the Shaggy Inkcap, is well worth knowing about. It has vaguely the same shape but is fatter and distinctly a brownish grey. It is edible, but only if you consume no alcohol at all for twenty-four hours either side of eating it.
The cause of this odd behavior is a chemical called 'coprine' which it contains in sufficient quantities to ruin a night out - or last night. Coprine is an acetylaldehyde dehydrogenase inhibitor. The liver breaks-down ethyl alcohol in stages, one of them produces acetylaldehyde but toxin prevents the breakdown of this unpleasant compound and it builds up in the bloodstream.
The unpleasant effects are effectively a terrible hangover in minutes. The US National Library of Medicine gives a nice run down of what there is to look forward to in a mild exposure: '...even small amounts, produce flushing, throbbing in head and neck, throbbing headache, respiratory difficulty, nausea, copious vomiting, sweating, thirst, chest pain, palpitation, dyspnea, hyperventilation, tachycardia, hypotension, syncope, marked uneasiness, weakness, vertigo, blurred vision, and confusion'. 'Death' is the last one on the list of severe effects, but such effects are extremely unlikely in the quantities found in the Common Inkcap.
Coprine syndrome is unusual in that two, generally benign, compounds must be in the body at the same time and the severity of the effect is determined by the levels of both. Unfortunately, it takes very little alcohol to cause nasty symptoms - even a few dabs of perfume behind the ear being enough.
Of course, it you are tee-total you will simply wish to know if it is good to eat. Sadly, since my last forty-eight-hour period on the wagon was circa 1959, I am unable tell you..