Mushrooms and Toadstools. Edible and Poisonous Fungi.
Mushrooms and Toadstools. (Edible and Poisonous Fungi.)—Notwithstanding the fact that it has been shown that edible fungi, when compared with other articles of food, do not possess a high food value, the interest in the study of the Fungi, as well as the consumption of edible forms, is constantly increasing. The study of the fungi is one of the most highly specialized, as there have been up to the present time no less than 64,000 species described. From a food standpoint the differentiation of the edible from the poisonous is one of the most difficult that the novice can undertake, as it is almost impossible to lay down any invariable rules.
The fungi are divided into a number of classes, each of which is again subdivided into sub-classes, series, and families. The family of Basidiosporeae include the largest and most conspicuous of the fungi and all of the mushrooms and toadstools. It is commonly believed that mushrooms are edible and that toadstools are poisonous; in reality, however, no such distinction should be made. The plants of the Hymenomycetes are characterized in general in that they arise from a mass of colorless threads, known as "mycelium" or "spawn," produced in the ground, bark of trees, etc. Their first appearance above ground is marked by the production of small solid balls (called buttons), which gradually enlarge, and at length shoot up into a stem or stipe bearing at its summit the umbrella top or "pileus," which is at first closed around the stalk like a closed umbrella and then expands more or less widely, according to the species. The under side of the pileus is the part which bears the spores, which correspond to the seeds of higher plants. In some cases the under surface consists of a series of gills resembling knife blades, which radiate from the top of the stalk to the circumference, like the spokes of a wheel, as in Agaricaceae; in others it consists of a mass of small pores or tubes packed closely together, side by side, as in Polyporaceae; in others of teeth, as in Hydnaceae; in others only slightly wrinkled or undulated, as Thelephoraceae, etc. The Basidiosporeae include about 14,000 species which are included in nine orders and subdivided info twenty-five families. A few of the important are the following:
1.—Agaricaceae (the mushrooms and toadstools proper) comprises about 4600 species, some of which are poisonous, as the Amanitas (Fly and Deadly Agarics) Lactarius (with a milky juice), whereas others are edible, as Agaricus (Psalliata) campestris L., the common mushroom, Cantharellus cibarius, Fr., etc.
2.—Polyporaceae (pore-fungi) includes about 2000 species, many of which are parasites on trees and destructive to timber; some are edible, as Boletus edulis Bull., whereas others are poisonous, as B. satana Lenz.
3.—Hydnaceae (teeth-bearing fungi); Most of the species are too small and woody to be eaten. Hydnum repandum forms "fairy rings" in woods.
4.—Thelephoraceae: Most of the species are small, and the larger species are tough and leathery.
5.—Clavariaceae (coral-shaped fungi) includes some large fungi; none are poisonous and some, as Clavaria flava Schaeff., are palatable.
Of these, the most important group are the Agaricaceae, both from the point of view of the toxicologist and the epicure.
It is not possible in this limited space to even mention the various poisonous and edible fungi that experience has demonstrated as such. The number of species which have been eaten or experimented with, however, is small compared to the number recognized by botanists. Many students of fungi have formulated rules for distinguishing edible from poisonous fungi. "The different popular tests for distinguishing edible from poisonous fungi, such as, for instance, the blackening of a silver coin or spoon when placed in a mass of poisonous fungi while they are being cooked, are all absolutely worthless." The only safe rule is to use no mushroom which the collector is not absolutely sure from previous experience is edible.
The common mushroom (Agaricus campestris L.. is practically the only species cultivated in this country, and is the only fresh species sold in the northern markets during the winter months. It is found wild in open grassy fields and pastures in great abundance in August and September. It is not common on the mountains, never found in woods, and never grows on trees or fallen trunks. The color of the stalk and pileus varies from a whitish shade to drab, but the color of the gills, a point which should never be overlooked, is at first pinkish and then a brownish-purple. The stalk is cylindrical and solid, and has, rather more than half way up, a membranous collar called the ring; but there is no membrane or scales found at the base of the stalk, which appears to come directly out of the ground. "In specimens which are not fully expanded there is a thin membrane or veil which extends from the stalk to the margin of the pileus. When the veil is ruptured, exposing the gills behind, a part remains attached to the stalk, forming the ring already referred to. In older specimens the ring shrinks, but generally a mark remains showing where it has been attached."
Two of the most poisonous forms resembling the common mushroom, and which have been eaten in mistake for it, are the deadly agaric and fly agaric.
The fly agaric (Amanita muscaria (L.) Pers.., so called because decoctions have been used for killing flies, is in some localities much more abundant than the common mushroom. It is seldom found in the grassy pastures preferred by the common mushroom, but more generally in poor soil, especially in groves of coniferous trees. "It grows singly and not in groups and differs from the common mushroom in having gills which are always white, never pink or purple and in having a hollow stem, which is bulbous at the base and clothed with irregular fringy scales on all the lower part. The pileus varies in color from a brilliant yellow to orange and a deep red, the yellow arid orange being more frequent than the red. The surface ia polished, and has scattered over it a larger or smaller number of prominent, angular warty scales which can be easily scraped off. The gills and stalks are white, and there is a large membranous collar which hangs down from the upper part of the stem."
The deadly agaric (Amanita phalloides (Pers.), Fr.., so named because it probably has been more frequently the cause of death than any other fungus, prefers a damper and less sandy soil than the fly agaric and is not pre-eminently an inhabitant of grassy pastures. "The pileus is often a shining white, but may be of any shade from a dull yellow to olive, and when wet is more slimy than the common mushroom or the fly agaric. It has no distinct scales and only occasionally a few membranous patches on the pileus. The gills and stalks are white, and the latter has a large ring like the fly agaric and is hollow, or when young, is loosely filled with cottony threads, which soon disappear. The base of the stalk differs from that of the fly agaric in being more bulbous and in having the upper part of the bulb bordered by a sac-like membrane called the volva. The volva is often of considerable size but more frequently it is reduced to a membranous rim."
The list of edible and poisonous fungi are relatively long, and while most belong to the Hymenomycetes, some are also yielded by the Gasteromycetes, as the puff-balls. The giant puff-ball, Lycoperdon bovista (L. giganteum Batsch), is found in the region of San Francisco Bay, not rarely forty inches in diameter.
We may conveniently consider the poisonous mushrooms in four groups following the divisions of Kobert. (Ueber Pilzvergiftung, 1891.)
In the first group is the genus Lactarius which owe their toxic properties to the presence of an irritant resin. Some of this genus, as L. deliciosus, are stated to be edible, but most of them produce severe or even fatal gastric enteritis.
The second group contains species belonging to the genus Helvellae, whose juice contains helvellaic acid, isolated by Boehm. It is asserted that these fungi, when thoroughly dried are not poisonous, and that hot water also extracts from them the poisonous acid, so that boiling makes them edible. The chief physiological action of the acid seems to be to destroy the red blood corpuscles, and, probably by such action, to produce vomiting, hemoglobinuria, jaundice, irritation of the kidneys, etc.
The third and most important group are the Amanitas. They are the most common source of mushroom poisoning, not only because of their resemblance to many of the edible species, but also because of the virulence of their effects. The most important of this specie is the A. phalloides, or skunk mushroom. According to Ford (J. P. Ex. T., 1910,1, p. 275), they contain two poisonous substances, one being hemolytic, and the other causing degenerative changes in the various internal organs, especially the liver, kidney, spleen and muscles. The Amanita-hemolysin, which is probably identical with the Phallin of Kobert, appears to be glucosidal, and because it is destroyed by heat, probably plays little part in human poisoning. The nature of amanita-toxin is not yet determined, but poisons of a similar nature appear to be widespread throughout the whole of the genus.
In the fourth group are included those which contain muscarine. This alkaloid was first obtained from the Amanita muscaria, but is also found in the A. pantherina, the Russula emetica, in Boletus luridus, B. Satanus, and, according to Ford (J. P. Ex. T., 1911, ii, p. 549), occasionally also in the Clitosybe dealbata, which has by some been classed as an edible fungus. Decoctions of the Amanita muscaria are used to poison flies, whence the common name of the fly agaric. The inhabitants of the Caucasus also use this fungus as an intoxicant. The A. pantherina is used in Japan for like purposes.
Muscarine was first obtained in a state of purity by Schmiedeberg and Koppe. (Das Muscarin, Leipzig, 1869.) The alkaloid may be produced artificially by gently heating choline platino-chloride with strong nitric acid. Potassium chloride is used to decompose the muscarine platino-chloride and produce muscarine hydrochloride; treatment with moist silver oxide yields the muscarine as a hydrate (C5H15O3NH2O). Muscarine resembles pilocarpine in its physiological action, and is antagonistic to atropine. It increases the secretions of the sweat, salivary and lachrymal glands, contracts the pupil, slows the pulse, and causes motor weakness. The reduction in the pulse rate is due to stimulation of the pneumogastric nerve, and after very large doses diastolic arrest occurs. If atropine be given so as to paralyze inhibition the cardiac movements reoccur. The vasomotor nerves are said to be paralyzed. There is a stimulation of the muscles of the intestines, bladder and spleen. Thus the intestines are transformed into hard, white cords, or afterwards, becoming somewhat relaxed, exhibit a tumultuous peristalsis. The abdominal secretions are greatly increased.
The symptoms of mushroom poisoning will vary greatly according to the special fungus which has been ingested. In the case of the deadly agaric (Amanita phalloides) which is the most common source of toadstool poisoning, the symptoms usually do not appear for several hours after the fungus has been eaten. They consist of great prostration and collapse, cold sweats, stupor, sometimes preceded by delirium, convulsions, frequently cyanosis and not rarely icterus. There is usually, also distinct fever and either hemoglobinuria or methemoglobinuria, and evidence of irritation of the kidney is shown by the presence of albumen, or partial suppression of the urine. When the poisoning is produced by fly agaric, to these symptoms will be added those of muscarine poisoning, namely, profuse salivation, contracted pupils and slowing of the pulse. In the poisoning by the lactarii the symptoms are those simply of violent inflammation of the alimentary tract, vomiting, purging and collapse. In poisoning by the Helvellae the symptoms resemble those produced by the Amanitas.
Little can be done to save the patient. Our utmost efforts should be directed to preventing absorption. A promptly acting emetic, such as apomorphine, should be administered to produce vomiting. Secheyon (P. J., 1910, liiiv, p. 492) highly recommends animal charcoal for the purpose of absorbing the poison, and thus preventing its entrance into the system. At least a table-spoonful, stirred up in water, should be administered, and repeated libitum. It is also advisable to administer atropine hypodermically in one-sixtieth-grain doses (1 mgm.), as it is the physiological antagonistic to muscarine, and may prove a life-saving remedy in poisoning by fly agaric, and by its general stimulant effect will also exercise a feeble influence in combating the collapse even although due to other forms of poisoning. A rapidly acting cathartic should also be administered to cleanse the intestinal tract. Aside from these measures, the treatment is purely symptomatic—the use of opium if necessary to check the diarrhea and vomiting, and various stimulants to maintain the circulation and respiration.
B. W. Richardson, having noticed that the smoke of the Lycoperdon Proteus or puff-ball was used for stupefying bees, found that the inhalation of the fumes caused various animals to become insensible. He has himself inhaled the fumes clarified by passing them through water, and experienced symptoms of intoxication and drowsiness. (M. T. G., 1853, 610.) Thornton Herapath, however, maintains, as the result of his experiments, that these anesthetic effects are in reality not owing to any narcotic principle present in the fungus, but to the carbon dioxide gas generated during their combustion. (Philos. Mag., July, 1855.)