104 



HA R D WICKE ' S SCIENCE-GOSSIP. 



Pontus, had made a special study of poisons, and had 

 even written a book on them. He accustomed his 

 body to the strongest of them by taking at first small 

 but gradually increasing doses, so as to protect him- 

 self against being poisoned. The opium-smoker can 

 stand a quantity of that drug that would be most 

 dangerous to us. 



In spite of these anomalies, the definition of poison 

 given above is probably correct, and keeping it in 

 mind we will now throw a rapid glance on the nature 

 of poisons. Poisons are represented in all the three 

 kingdoms of nature ; there are, therefore, animal, 

 vegetable, and mineral poisons. And without taking 

 into account the kingdom from which they proceed, 

 poisons may be again divided by the different modes 

 of action of their deleterious effects. Those called 

 acrid or irritants act by inflaming the parts with 

 which they come in contact. The plants whose 

 poisons belong to (his class are the spurge, colocynth, 

 savin, most Ranunculi, the meadow-saffron, water- 

 dropwort, etc. The narcotics, without producing 

 any immediate change on the surface exposed to 

 them, act on the brain and nerves, inducing a ten- 

 dency to insensibility and torpor. The principal are 

 the henbane, bitter-sweet, Lactuca virosa, and all 

 plants containing opium or prussic acid. The third 

 class, that of the narcotic-irritants, partakes of 

 the qualities of the other two classes, and comprises 

 the strongest poisons. The most common plants of 

 this class are the deadly-nightshade, thorn-apple, 

 tobacco, foxglove, hemlock, cowbane, ' ! nux vomica," 

 and the poisonous fungi. Camphor, turpentine, 

 ether, and alcohol also belong to these. 



The toxic properties of plants are due to certain 

 substances contained in them, most of which have 

 already been studied and extracted by chemists. 

 These substances are generally of an alkaline nature, 

 and called alkaloids ; some are acid. The vegetable 

 kingdom produces about iooo alkaloids, of which 

 about 200 have become at all accurately known — a 

 good number, considering that their existence was 

 discovered only three quarters of a century ago, i.e., 

 by Lerturner in 1816. Most of them are violent 

 poisons ; amongst the best-known I may name 

 morphine, codeine, strychnine, aconitine, nicotine, 

 coneine, atropine, hyoscyamine, etc. The acids are 

 either united to alkaloids or to oils. 



There are various ways by which these poisons may 

 be accidentally introduced into the system. Through 

 the nose, in the form of odours ; through the lungs, 

 by inspiration ; by the mouth, in the form of food ; 

 through the skin, by absorption ; and, very readily, 

 by recent wounds. They act either on the nerves, 

 and brain, on the blood, or on the tissues of the body. 

 Opinions seem to differ as to whether poisoning 

 in general takes place primarily through the nerves 

 or through the blood, and facts are brought forward 

 to support both theories. It is, for instance, said on 

 'he one hand, that after cutting the gastric nerves no 



poisoning takes place in some cases, and that a solu- 

 tion of emetic tartar, if injected Into the veins causes 

 nausea in the stomach by acting through the nerves. 

 On the other hand, it is stated that prussic acid, 

 which otherwise acts on all tissues, animal and vege- 

 table, has no influence whatever if brought in contact 

 with the nerves only. Strychnine produces no effect 

 unless it gets into the blood, as the celebrated German 

 physiologist, J. Muller, proved by the following in- 

 teresting experiment that poisoning cannot take place 

 through the nerves alone. He exposed the nerves of 

 the legs of some toads, so that the calf and thigh were 

 only connected by the bones and nerves. Then he 

 placed the legs for a long time in an acid solution of 

 morphine and a concentrated solution of opium. 

 Many hours afterwards the. toads were still alive and 

 perfectly sensible. 



It seems, however, that poisons in general, which- 

 ever way they may be introduced into the body, kill 

 by finally acting on the brain through the nerves. It 

 is worth noticing that opium, morphine, belladonna, 

 alcohol, etc., chiefly act directly on the brain ; 

 strychnine, tobacco, and camphor on the spinal 

 chord ; aconite, cicuta, colocinth, and colchicum on 

 the ganglion system. The upas and wourali poisons, 

 like that of venomous snakes, act by altering and 

 decomposing the blood. 



Of all poisons, those of vegetable origin are perhaps 

 the most common and certainly the most violent. 

 Unfortunately they are also the most difficult to 

 determine, for whilst nearly all mineral poisons are 

 well-known and comparatively easy to analyse, and 

 the poisons of animals readily obtained in a pure 

 state for study, the poisons produced by plants can 

 only be extracted after a lengthy process of distillation 

 — too lengthy, indeed, and besides too varied, to be, 

 described here. The toxic agents of many plants 

 have not been discovered yet, and of those that are 

 known, only a few, such as strychnine, morphine, 

 brucine, etc., have been subjected to a thorough 

 study. The result of this is, that whilst there are 

 numerous tests by which to identify mineral poisons, 

 the determination of the vegetable alkaloids is, 

 mostly, very uncertain. The toxic products of plants 

 are determined by two methods, i.e., by their reaction, 

 when subjected to certain chemical agents or to the 

 blow-pipe, and by a microscopical examination of 

 the crystals of the alkaloids. As to chemical tests 

 the following may be of interest : — 



Iodic acid stains all vegetable alkaloids brown. 



Morphine gives a blue stain with chlorate of iron 

 or gold ; sulphuric acid turns it first yellow and then 

 red. 



Strychnine. — Sulphocyanide of soda, if introduced 

 into a solution of strychnine, soon causes the crystal- 

 lisation of the alkaloid. 



Veratrine is turned milky by the same reagent. 



Emetine is turned milky by the same reagent, and 

 yellow by chlorate of platinum. 



