all folks the most sceptical, is thus far unconvinced of its value, and awaits the results of a larger number of cases; feeling, meanwhile, at full freedom to test its possible utility in a disease so unconquerable by ordinary methods.

The poisonous agents which have power to destroy life by acting directly on the heart are numerous. Among them we find aconite and digitalis well known as medicines, and useful to control tumultuous or over-excited activity in this essential organ. Several, also, of the Eastern arrow poisons belong to this class, -as the upas, of Borneo; and, finally, the corroval, an arrow poison of the Isthmus of Panama.

To point out precisely in what way these various agents influence the heart would require us to explain at length the whole physiology of this organ, and to discuss the function of the different nerves which enter it. We shall therefore content ourselves with relating what is known in regard to corroval,

a poison which thus far has been investigated only by two American toxicologists. Like woorara, this substance is a resinous-looking material, which is certainly of vegetable origin. It is used as an arrow poison by the dwellers on the Rio Darien, but of the nature of the plants which yield it we know absolutely nothing. Thus far it is known only to savages, and to two or three students of poisons, nor, if it were used to kill man, would it be possible to detect it in the tissues. As in the case of woorara, let us relate briefly how the toxic characters of corroval were first investigated.

A frog was held while the operator placed a morsel of poison in a wound made in the back. In ten or twelve minutes it showed signs of lassitude, and in half an hour was totally motionless and dead. Nothing was seen to lead to the belief that the toxicologist was dealing with a substance differing from common woorara. The outward signs were alike. A second frog was then poisoned, after a little V-shaped opening had been so made as to expose the heart, whose natural beat

was noted as being forty-five to the minute. In three minutes it was unaltered as to number, but had become irregular. Then it began to fail, beating thirty at the fifth minute, and ceasing half a minute later, the auricles continuing somewhat longer. As the organ failed, a strange fact was noted; at the instant when the great cavity of the heart the ventricle contracted so as to expel the blood into the arteries, it was observed that here and there on its surface little prominences arose, which were presumed to be due to these parts being palsied so that they yielded under the pressure from within. That this was a true view of the case was shown by pinching or galvanizing minute portions of a healthy, active heart, when the same appearances were noted at the points enfeebled by the over-stimulation to which they had been thus mechanically subjected. When the heart stopped, it could not be re-excited by a touch, or by electric currents, as was the case in woorara poisoning, or in death from violence.

During all of this time, and for twenty minutes after the heart ceased to beat, the frog leaped about with readiness and ease, so that it seemed pretty clear that corroval was a poison which paralyzed directly the tissues of the heart, without at first influencing any other portion of the economy. To put this beyond doubt, the experimenter tried to keep up the circulation by causing artificial breathing, which in the case of woorara was competent to sustain the heart's action. Here, however, the heart stopped as though no such means had been used. The same observation may be better made on the young alligator, because in this creature the breathing continues for some twenty minutes after the heart has ceased to pulsate, thus making it still more clear that the heart does not die owing to defect of respiration. Lastly, it was shown that when in a healthy frog the heart is cut out, or its vessels tied, voluntary and reflex motion disappear at about the same period as they do when corroval has been given; whence it was inferred that this agent

destroys the general movements only because it first interrupts the circulation of the blood, without which they soon cease to be possible.

The contrast between woorara and corroval is very striking, since in the former the heart dies last, and in the latter it is the first organ to suffer.

We are aware thus far of scarcely a poison which acts entirely on a single organ. In every case it has been found that the noxious effects are finally felt by other parts in turn; and, so far as we can gather, these secondary poisonings are direct effects of the poison in many cases, and not merely results of the death of the organs first injured. Thus, while pointing out that in the reptile voluntary motion exists after the heart stops, but soon ceases on account of the arrest of circulation, we might have added, that, by a variation in the mode of experimenting, it can be made clear, that where, owing to a small dose of the poison, death comes slowly, the sensitive nerves first, and then the motor nerves, and last the muscles, are all directly and in turn affected by the poison. Finally let us add, that, given by the mouth, this agent usually causes convulsions, such as do not appear if the poison be put under the skin, fact for which we cannot in any way account, but which aptly illustrates how easy it is to deceive one's self where such variations may arise in the symptoms caused by one and the same poison.

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As an apt illustration of the difficulties which surround this study, it may not be out of place to mention the following incident. During the study of corroval it became desirable to learn the rate at which this material could be absorbed from the stomach. Accordingly a weighed morsel was pushed down the wide gullet of a large frog and into its stomach. The animal being left in a vase with a half-inch of water, the next day it was alive and well, to the operator's surprise. Repeating the experiment, the frog was left under a bellglass, on a dry plate. This time the corroval was found on the plate, so that

it seemed to have been vomited, as to which operation as possible in a frog nothing had been hitherto known. The following day a full dose of corroval in a little alcohol and water was poured through a tube into the stomach, when instantly this organ was inverted, and pushed up through the wide gullet and outside of the mouth, where the frog presently cleaned it most expertly with its fore legs. Its return was gradual, and over this act the creature seemed to possess no voluntary control.

As the power to turn the stomach inside out is rarely exercised, and therefore not anticipated, the reader may understand how easily it might deceive, if a poison having been given it were thus disposed of in the experimenter's absence.

A favorite mode of suicide in France is to breathe a confined atmosphere in which is burning a pan of charcoal. For a long time it was supposed that, under these circumstances, the death which ensued was due to the carbonic acid set free as one of the products of combustion, in which case we should have asphyxia from deficiency of oxygen and excess of carbonic acid, - a mode of death as well understood as any death can at present be.

When, however, attention was called to the presence of another gas, in the mixed products of incomplete combustion, the toxic characters of this agent, now known as carbonic oxide, became subjects of inquiry. After several theories had been set forth, only to be pushed aside by the next comer, Claude Bernard re-investigated the matter, and, with his usual happiness in discovery, pointed out what is, at least for the present, a well-accepted explanation of the mode in which this gas poisons.

Here for the first time we deal with an agent which enters the blood through the lung. Six hundredths of the volume of an atmosphere, the rest of which is common air, is fatal to a bird confined within it. The death is rapid, and usually convulsive. Upon examining the body of the poisoned animal, we are

struck with the brilliant red color of the blood; and if at the same time we compare the appearances seen in a bird killed by carbonic-acid gas, we shall be still more impressed with the difference, because this latter gas colors the blood of a very dark hue.

To make clear what is to follow, the reader should carry in mind the following facts. The blood, in circulating, goes through the lung, and there gives up carbonic acid, and, receiving oxygen from the air, becomes bright red. Thus altered it is forced by the heart along the great arteries, until, finally entering the minute vessels called capillaries, it has between it and the tissues only walls of the utmost thinness. This vast mesh of tiny tubes makes the great markets of the body, in which occur a host of exchanges, of givings and gettings on the part alike of blood and tissues, such as muscle, nerve, and bone. The most important of these is the taking of oxygen by the tissues, and the giving up of carbonicacid gas to the blood. The first gas is needful for a multitude of purposes, without which life must cease; the second, when retained, is poisonous; and, as the interchange depends for existence ' upon there being two gases, the loss of a hurtful one is made subservient to the getting of a useful one. Moreover, as the little blood rivers flow by nerve and bone, the materials which these must get rid of as the results of their waste are cast for the most part into the general volume of these streams; but, as regards the gases, we find them transported chiefly on or in the blood-globules, which float in myriads along these tiny streamlets. In the tissues they each get a load of carbonic acid, of which they lose the most in the lungs, replacing it with oxygen, and so are continually voyaging to and fro betwixt the sources of supply and demand. Imagine for a moment these millions of little carriers become incapable of transporting their destined freights, and such precisely is what occurs when an animal is made to breathe carbonic oxide gas.

Healthy blood shaken with carbonic acid becomes dark, and fresh contact with the air will redden it again. When once it has been poisoned by carbonic oxide, such changes are no longer possible, simply because the blood-globules have grown incapable of taking up any gas but the one which has poisoned them.

Neither can we cause them in any way to give up the hurtful carbonic oxide which has taken possession of them. A fatal attachment has been formed, and they refuse to return to their everyday duty.

The careful and elaborate series of analyses and experiments which brought Bernard to this conclusion it would be folly to attempt to make clear to any but the physiological chemist. So far they have not been set aside by any more authoritative verdict.

Here, then, we have the curious case of asphyxia, or death from want of oxygen, not because the lungs have ceased to present it to the blood, but because that fluid has become unable to accept the gift.

Hence results sudden cessation of every function which demands for its continuance unceasing change in the tissues which effect it, and so death follows as a matter of course.

I cannot hope that to any but very careful readers I may have been so happy as to make clear the history of these three poisons, as they act within the body, and sunder one or another of the many essential links which make the complete chain' of life. One abolishes the power of the nerves of motion; one palsies the muscles of the heart, and one annihilates the function of the red blood-globules. These diverse modes of destructive activity are but instances of the wonderful variety of modes in which the fortress of life may be assailed.

The reader will not fail to have noticed that two of the three poisons here discussed are of comparatively recent introduction.

The same statement applies to the two best-known kinds of upas, and to a third, admirably studied by Dr. William A. Hammond, while the

same may be said of Calabar bean and other poisons used by savage tribes. Scarcely one of these could as yet be detected in the body of man, were it employed to destroy life; so that it is as well that these dangerous agents should be carefully guarded by the toxicologists into whose hands they may chance to fall. A recent writer in these pages, alluding to this subject, also points out that the same difficulty in detection applies to many of the poisonous substances which every year are made by chemists engaged in the study of complex organic compounds. Some of the bodies thus discovered are of the most deadly character; so that here again it is well that the awful power which they give should rest in the keeping of the trustworthy men of science whose industry has brought them to light. Poisoning, as a rule, has been a crime of the intelligent classes, rather than of the poor, or of those whose passions, being under less certain government, are apt to seek gratification by the most direct means. Of late, however, it has become so well known to educated persons, that the more ac

cessible poisons are sure to be detected by the chemist, that I have no doubt this alone has tended to lessen their fatal use. The question of the relative ease with which poisonous drugs may be obtained leads to some reflections which have especial application in our own country.

In Europe, and particularly on the Continent, the sale of poisons is surrounded by the most stringent precautions, so that it is very difficult to procure them without a physician's prescription; the doctor, as it were, coming between the apothecary and the public, to guard the latter from crime or injury. Here, however, the utmost laxity prevails, and although in some States rigid laws on the subject exist, they are daily disobeyed by almost every druggist,