Popular Science Monthly/Volume 26/March 1885/The Painless Extinction of Life



DURING the latter part of 1883 and the early part of 1884, I constructed at the Dogs' Home, Battersea, at the request of the committee of that institution, a lethal chamber for the painless extinction of the life of the animals which have, of necessity, to be destroyed there. I put the process first into operation on Monday, May 15th, by subjecting thirty-eight dogs to the fatal narcotic vapor. They all passed quickly into sleep, and from sleep into death. Since that time, for a period of seven months, the lethal chamber has been regularly in use. From two hundred to two hundred and fifty dogs per week have been painlessly killed in it, or a total of nearly seven thousand.

The thought of applying the anæsthetic method to the painless destruction of the lives of the lower animals, and the first accomplishment of it, came from myself, and dates back as far as the year 1850. In that year, I constructed at Mortlake, where I was then starting in practice, a small lethal chamber, to which my neighbors would frequently bring animals which they wished to have killed. In 1854 I began to illustrate this mode of painless death, and from that time up to 1871 I never allowed the subject to rest. In 1871 I brought it formally before the Medical Society of London. About this same time I made a communication to the Royal Society for the Prevention of Cruelty to Animals, and suggested a mode for killing painlessly dogs and cats that were wounded in the streets. From that time I have continued the inquiry, making use of all the known anæsthetic substances, in order to ascertain which was cheapest, most adaptable, most certain in action. The information thus obtained proved very useful when the time came for utilizing it.

In undertaking the practical act of carrying out lethal death on the large scale required at the Home, I had to determine, in the first place, on the anæsthetic or anæsthetics to be used; and, in the second place, to construct the room or chamber in which the animals should be confined while exposed to the lethal gas or vapor. I have placed on the wall a table of anæsthetics, including most that have up to this time been discovered, with a general outline of their respective properties and values. There is, you see, a goodly list, twenty-two in all. Out of these I selected, as shown by experiment to be the best, four: Carbonic oxide, chloroform, carbon bisulphide, coal-gas.

Carbonic Oxide.—I was led to carbonic oxide, not only by reading of it, and by witnessing the effects of it as a poison when it has been breathed from coke-fumes, but specially from studying its action when


Gas or vapor
density H = 1°.
Fluid density,
water = 1°.
Cent. Fahr.
Deg. Deg.
Nitrous oxide NO Gas 22 . . . . . . . . Supports common combustion; sweet, and not irritating to breathe.
Carbonic oxide CO Gas 14 . . . . . . . . Burns in oxygen; not irritating to breathe.
Carbonic acid CO2 Gas 22 . . . . . . . . Extinguishes flame; irritating to breathe.
Bisulphide of carbon CS2 Fluid 38 1∙270 43 107 Vapor burns; odor disagreeable unless well purified.
Hydride of methyl (marsh gas) CH3H Gas 8 . . . . . . . . Burns in air; inodorous, not irritating.
Methylic ether C2H6O Gas 23 . . . . . . . . Burns in air; almost inodorous when pure.
Methylic ethyl ether C2H6O Fluid 30 . . . . 11 52 Burns in air; ethereal odor; rather pungent.
Chloride of methyl CH3Cl Gas 25∙25 . . . . . . . . Burns in air; rather pungent.
Bichloride of methylene CH2Cl2 Fluid 42∙5 1∙320 40 104 Vapor burns; pungent odor.
Chloroform CHCl3 Fluid 59∙75 1∙480 61 142 Vapor extinguishes flame; pungent odor.
Tetrachloride of carbon CCl4 Fluid 77 1∙560 78 172 Vapor extinguishes flame; odor fragrant, not pungent.
Hydride of ethyl C2H6H Gas 15 . . . . . . . . Burns in air; inodorous.
Ethylic ether (absolute ether) C4H10O Fluid 37 ∙720 34 93 Burns in air; pungent to breathe.
Chloride of ethyl C2H5Cl Fluid 32∙25 ∙921 11 52 Burns in air; ethereal odor; rather pungent.
Ethylene (Olefiant gas) C2H4 Gas 14 . . . . . . . . Burns in air; pleasant to breathe.
Bichloride of ethylene (Dutch liquid) C2H4Cl2 Fluid 49∙5 1∙247 80 176 Vapor burns; ethereal odor; rather pungent; smoky.
Chlor-ethylidene C2H4Cl2 Fluid 49∙5 1∙174 64 147 Vapor burns; ethereal sweet odor; pungent.
Bromide of ethyl (hydro-homic ether) C2H5B2 Fluid 54 1∙400 40 104 Vapor rather pungent, but pleasant.
Hydride of amyl C5H11H Fluid 86 ∙625 30 86 Vapor burns in air; inodorous when pure.
Amylene C2H10 Fluid 35 . . . . 89 102 Vapor burns in air; pungent; smoky.
Hydrocyanic acid HCN Fluid . . ∙705 26 72 Vapor painful to breathe; special; suffocating odor.
Coal-gas . . . . . . . . . . . . . . . . . . Gas at first slightly irritating, but quickly narcotic.

evolved from the fumes of the Lycoperdon giganteum, or common puff-ball. The fumes as thus evolved have been employed for centuries past by the common people for narcotizing bees before taking the honey from the hive. A portion of the substance being burned under the hive, the bees, inhaling the fumes, fall into a deep sleep, during which time they are unconsciously deprived of their industrious earnings. I was so struck with the perfect action of these fumes after being shown one of these experiments, that, in 1854, I introduced the fumes for anaesthetic purposes. Purified by being passed through water, they produced the most rapid narcotism, under which many operations were performed painlessly on the inferior animals. The question was the character and chemical nature of the agent in the fumes which produced the anæsthesia. The late Dr. John Snow, so well known for his immense labors on anæsthetics, and the late Mr. Thornton Herepath, one of our most promising chemists, were each separately engaged in discovering the concealed gas or vapor. Snow and Herepath simultaneously, but by quite different methods of research, arrived at the fact that the narcotic present was carbonic oxide, or the same gas as is produced during the combustion of carbon or coke in a limited supply of oxygen.

These researches led me to study the action of this gas in its pure form, and to the discovery of many curious facts relating to it. Among other things, I noticed that, like oxygen, it made the venous blood of a bright-red color, and that warm-blooded animals exposed to it for a long period of narcotion are rendered temporarily diabetic.

I did not, on the whole, think it commendably safe as an anæsthetic for man, but I fixed upon it at once as one of the best and cheapest of lethal agents for the painless destruction of life in the lower creation. It is the principal agent for this purpose which I have used since the date named above, 1854.

Carbonic oxide is a gas, and, if quite pure, is so odorless and produces so little irritation that, when present in the air, it is apt to be breathed unconsciously until the effects of it are felt. Those who by accident have been narcotized by it, and have recovered from the effects, have expressed that they had no recollection of anything whatever, that they passed into sleep in the ordinary way of sleeping, and knew no more.

Chloroform.—I was naturally led to chloroform, by reason of its common use as an anæsthetic. There is no anæsthetic more certain in its action, and none more certain to kill if it be administered in a determinate manner. Administered even with skill, so as not to kill, it proves accidentally fatal about once in twenty-five hundred times, and, so soon as air is charged with over five per cent of its vapor, it is not breathed without danger. Death from it is very determinate when it occurs, and seems to be entirely painless. The vapor of chloroform does not burn; on the contrary, it extinguishes flame. If we plunge a lighted taper into a jar through which the vapor of chloroform has been diffused, the light is at once extinguished. When we use it for narcotism, we merely diffuse the fluid into the state of vapor, and make provision for the vapor to be absorbed by the lungs of those subjected to it. It produces little irritation when breathed.

Bisulphide of Carbon.—The bisulphide of carbon is a very rapidly acting anæsthetic. It produces narcotism, in fact, almost as quickly as carbonic oxide, and with less muscular commotion. The vapor of it burns in air if a light be brought near to it; but, when its vapor is mixed with that of chloroform, this danger is avoided. It is bought as chloroform is, in the fluid state, and can be obtained, therefore, from the chemist directly, ready for use, by diffusion of its vapor. It has one immense advantage, that of being excessively cheap; and it has one great disadvantage, that of being excessively unpleasant in regard to its odor, unless it be most carefully purified by repeated distillations. Combined with chloroform, with which it mixes freely, the peculiar odor is largely reduced, and, by pouring the mixture over chloride of lime, is almost entirely removed. For this reason, together with that relating to the difficulty of combustion of the combined vapors, I have used largely in these researches the mixture of chloroform and carbon bisulphide. The combined vapors produce also a singularly good antiseptic atmosphere.

Coal-Gas.—Common coal-gas is one of the most potent of narcotizing gases. It is a compound of four gases, three of which are excellent narcotics, and one a negative gas—forty-seven per cent of hydrogen, forty-two of marsh-gas, three of heavy hydrocarbons, and eight of carbonic oxide. All these gases are anaesthetic in their action: marsh-gas is one of the best, and carbonic oxide is one of the quickest; but they are all explosive.

For the lethal purpose, nothing could possibly surpass coal-gas. I put it freely to the test, and found it was all that we could desire. In an atmosphere containing twenty-five per cent of this gas, an animal goes to sleep in from two to three minutes, and dies asleep as easily as in any narcotic vapor or gas whatever. The gas is always at hand, and for the present purpose is the cheapest and readiest of all. Under such circumstances, it seems absurd to think of going any further for a narcotic agent. And yet it is necessary, at all events, when a large lethal chamber is wanted, on account of the danger from explosion. All things considered, I was led to conclude that carbonic oxide was the best narcotic agent to employ, combining it with chloroform or carbon bisulphide, if that should prove necessary. Deciding on this point, the next question was how to manufacture the carbonic oxide so as to bring it into practical use on the easiest as well as the largest scale.

After making some unsatisfactory experiments, I luckily recalled Mr. Clark's condensing-stove. This is a most ingenious invention. The fumes proceeding from the combustion in the furnace first ascend and then descend through two lateral columns, to escape by a tube directed over a trough or saucer. A large quantity of water-vapor is in this way condensed, and is collected at the base of the stove, together with substances derived from the combustion, which are soluble in water. Here, with a little modification, was what I wanted. To adapt the stove to my purpose, I got Mr. Clark to make a charcoal furnace over a gas-burner, so that, when the charcoal was laid in the furnace, it could be instantly set alight by merely turning on and lighting the gas, letting the flames of gas play through the charcoal. Next I got him to make a large condensing cistern beneath the stove, with an opening from it to convey the carbonic oxide by a tube into the lethal chamber, and with a tap, by which the condensed fluid could be drawn off. The arrangement answered straight away, if I may so say. The immediate combustion of the charcoal by the gas yielded very nearly the theoretical value of the product, carbonic oxide. The gas was deprived of water by the condensation; it was delivered over to the chamber with a steadiness sufficient for all practical necessities; it was cooled without any other artificial means, so as never to raise the chamber above summer heat; it was produced cheaply; and it afforded such simple action that any workman could at once learn to use it. Another useful result springing from the employment of this stove was, that it enabled me to diffuse other narcotics into the chamber, by merely allowing the warm gas proceeding from the stove to pass over a porous surface, charged with the narcotics, on its way into the chamber.

To apply the narcotic gas or vapor, it is necessary to have a closed place in which the animals are exposed to the narcotic, and another place in which they are collected preparatory to being subjected to the narcotism. This implies what I have called the lethal chamber, and a cage. At Battersea, it was necessary to have an apparatus large enough to narcotize as many as one hundred dogs at a time. It was, therefore, essential to have a large lethal chamber, and one that was strong and effectively constructed. I noted down at the beginning the following requirements, all of which I had calculated out of a series of preliminary studies, and constructed on a small working scale.

1. The chamber, of whatever substance built, must be so constructed that its interior shall not be subject to great variations of temperature. This I knew to be very important, since, in observing the action of narcotic vapors on the human subject, I had learned that humidity and cold materially interfere with their quick action, while dryness and warmth favor such action. In a lethal receptacle, such as was being constructed, there could be no certainty whatever, unless the temperature and dryness were at all times uniform.

2. It was necessary so to construct the chamber that sufficient but not an excess of room should be allowed in it for the expansion of the gases introduced. It might seem at first sight, and before inquiry was instituted, that the more the space within the chamber was reduced the quicker would be the effect. This, however, is not practically the fact. In order to secure perfect diffusion of the narcotic atmosphere, the space to be filled with it must be about one eighth greater than is absolutely required for a cage, fully charged with the animals that have to be killed.

3. Much care is required in connecting the stove with the chamber, so as to make sure of equal diffusion of the gases or vapors through the inclosed space. Unless this equal diffusion is rendered effective, some of the animals are more exposed to the vapors than others, and the effects are irregular, which is as bad a result as could possibly be obtained.

4. It was essential to provide that a sufficient quantity of the narcotic should be introduced before and for a brief period after the introduction of the animals.

5. It was requisite to invent a plan by which the chamber could be kept completely closed until the precise moment when the animals have to be introduced, then instantly opened for the introduction, and as instantly closed after the introduction. It was equally requisite to guard the entrance into the chamber, so that the men employed in pushing in the cage should be protected from the vapor. A method had also to be adopted by which it could be known when all the animals had ceased to breathe.

To meet the first of the above-named conditions, I constructed the lethal chamber (the outline of which is shown in Fig. 1) of well-seasoned

Fig. 1.—The Lethal Chamber.

timber, making every part of it a double wall, and filling the interspace closely with sawdust.

In order to obtain the slight excess of space which was wanted to insure diffusion, I formed on each side of the chamber an extra space, which I call a pocket. They are in the center on each side, and stand out as aisles from a central nave.

In order to secure quick and equal distribution of the vapors through the chamber from the stove, I let the gases in at first from the top, under the impression that the gases, being heavier than the atmosphere, would be made to pass with greater rapidity into all parts. Theoretically, this view is correct; but, as it became necessary to have two floors or tiers to the cage, I was obliged, in the end, to let in the gas half-way down the sides of the chamber. By using two stoves, one on each side, this method of introduction was both convenient and effective. To remove the common air, an opening, with a shaft of ten feet, was made in the roof. The shaft has a bore of three inches, and has a cap at the top, in order to prevent down-currents of air. At the foot of the shaft is a damper, which can be opened and closed at pleasure.

To meet the fourth necessity, a plentiful supply of the narcotizing vapor, two stoves have been connected with the chamber, each capable of burning two pounds of charcoal per hour, and giving up the products of the combustion into the chamber.

To make the narcotic effect still more certain, and to keep the chamber at all times lethal, I made an extra provision. At the two points where the tubes from the stoves enter the chamber, I have interposed two strong boxes made of elm, and covered with thin lead. These boxes, which are eighteen inches long and four inches broad, are filled loosely with the porous burned loam known as Verity's patent gas-fuel, an excellent substance for filling a grate where coal-gas is burned instead of fuel. This substance is so porous, it takes up narcotic fluids most readily, holds them in its pores, and gives them up in volumes of vapors when warm gas is passed over it. Into the boxes closed in with this fuel there is a funnel, opening at the top, for supplying the fluid, which can be shut with a stopper; and at the end of the box, standing out at a right angle from it, is a continuous section, in which there is a large tap, for regulating the currents of gas from the stove.

When the stoves are in action, the tap is turned on, and the gases from the stove pass through the boxes over the patent fuel into the chamber. Nothing more is done until just before the time when the animals in the cage are to be introduced. Then ten fluid ounces of an anæsthetic mixture, consisting of equal parts of methylated chloroform and carbon bisulphide, are poured upon the fuel through the openings in the top of the little boxes, the openings being immediately closed. After the animals are in the chamber, ten ounces more of the same mixture are added, and if, after three or four minutes, any of the narcotized animals are still breathing, ten or twenty fluid ounces more are poured in.

In pushing the charged cage into the chamber, there is naturally a very great displacement of gas or vapor within. It was necessary to provide an exit which would save strain on the walls of the chamber, and would let out a little gas without letting in common air. I met the problem by the plan shown in Fig. 2, which exhibits the chamber in section. Two feet from the far end of the chamber there is suspended from the top a light hanging screen, which reaches within four inches of the floor. Behind this screen, and in the roof of the chamber, is a shaft, with a valve opening upward. As the cage is pushed in, this screen is raised from the bottom, and the air, rushing out at the lower part, ascends behind, and escapes by the valve. The screen is so balanced that, when sufficient air has been extruded, its lower end reaches the back or lower end-wall of the chamber. It thus acts as a regulating valve, and, when the pressure is off, it returns to its level, letting any gas at the rear of it return toward the cage.

To enable the operators to introduce the cage quickly, and at the same time to protect them from the action of the vapors, the following plan, also indicated in the section diagram, is adopted. The door or entrance into the lethal chamber is a slide like the sash of a window. It is placed between two strong uprights, and is balanced by a weight and pulley in each, so that it can be opened and closed with the greatest rapidity. Behind this sliding door there is placed what I call the

Fig. 2.—Reduced Section of Fig. 1. Fig. 3.

shield or block; a framework of wood with four large metal valves, two opening inward, two outward. The shield is fixed on a base with four little wheels, and runs easily up or down the chamber. When the sliding door is raised, the movable valved shield is in position half a foot within the chamber, and cuts off all escape of vapor. The workmen thus have time to push the cage leisurely, after the door is raised, into the chamber, until the end of the cage touches the screen. This effected, they push the cage in a few seconds into the lethal atmosphere, the shield running before it, and then the door is slided down into its place. When all is nicely adapted, a very few seconds are required to introduce the cage and close the sliding or entrance door. When the cage is drawn out the shield is drawn out with it, by means of a cord which is attached to it, and which runs under the cage.

The last requirement which had to be met was the means of knowing when the narcotized animals had ceased to breathe. To get at this fact, the test of hearing was found to be the best. There is inserted into the chamber on one side a long stethoscope, made of bamboo; the mouth of this tube—of trumpet-shape—is in the center of the chamber, just above the cage, when that is in place. The outer part, or ear-piece, of the tube stands out four inches on the outside, and is closed when not being used, by a solid plug. On listening through this tube, the continued breathing of even a single animal can be detected, and the operators are enabled to determine if it be proper to increase the strength of the narcotic atmosphere, or to stop it.

In Fig. 4 will be seen best a description of the cage in which the animals are collected before being put into the lethal chamber. It is made of a wooden framework, with light iron side-bars. It has two sliding doors at the sides, two at one end, and one at the top. It can be filled and emptied through these doors with great rapidity. In order to hold as many animals as possible without discomfort to them, the cage is divided into two divisions or tiers, the flooring of the upper tier being freely perforated with openings, so as to establish a communication

Fig. 4.—The Cage.

between the upper and lower divisions, and allow a due distribution of the gases and vapors used. The cage runs on four eight-inch wheels, which are underneath it, and ply on galvanized iron rails.

The mode of death to which the animals are subject is that by anæsthesia, not by suffocation or asphyxia. Physiologically, there is a distinctive difference between these modes of death. Death by anæsthesia is death by sleep; death by asphyxia is death by deprivation of air. Death by anæsthesia is typically represented in death by chloroform; death by asphyxia is typically represented in drowning, or in immersion in carbonic-acid gas. When properly carried out, death by anæsthesia is by far the most certain and least violent of the two processes, although both are probably painless. It is worthy of record, however, that all animals are not equally susceptible to the action of the narcotic vapors. Cats, for instance, lie asleep much longer than dogs before they cease to breathe. They fall into sleep as rapidly as dogs, but do not pass so quickly into the final sleep. There is a difference between different animals of the same kind. Some dogs die almost instantly—in fact, as they fall asleep; others fall asleep and continue to sleep for several minutes before they cease to live. In the first observations, before I had rendered the narcotic atmosphere over-poweringly active for all cases, there were a few instances, nine in the first seven hundred, in which the animals slept on from half an hour until an hour after all their comrades had died. Finding out this strange peculiarity, I increased the amount of narcotic vapor until all succumbed very nearly at the same minute, and in the last six thousand there has been no recurrence of the prolonged insensibility. The animals are now commonly all asleep in from two to three minutes, and have ceased to exist in a further period of the same duration.

In Fig. 5 there is shown a view of the portable lethal chamber ready for use. It takes the shape of a closed truck on two wheels, and movable like a truck or barrow. It measures five feet in length, is two feet wide, and two feet six inches high. It moves very easily,

Fig. 5.—Portable Lethal Chamber.

and can be managed by one man. It is constructed, like the large lethal chamber, of well-seasoned wood, in double wall, with sawdust filling up the interspace. In Fig. 6 the apparatus is shown in section. There is one large chamber, having a capacity of nine cubic feet. The chamber opens at the top by a strong lid, swung from behind, which.

Fig. 6.—Section of Portable Lethal Chamber.

when brought down, entirely closes it up. Under this lid there is a frame with an opening in the center, through which baskets or cages of different sizes, and containing the animal or animals, can be let down into the larger space and held there. This larger space is the narcotizing receptacle or chamber.

At the back of the apparatus is a recess in which are placed the narcotizing fluid and the pump for forcing it into the cages containing the animals. The narcotic fluid is contained in a large, strong Wolff's bottle filled loosely with Verity's fuel. The forcing-pump is worked by a piston from the outside, and consists of a cylinder capable of containing one eighth of a cubic foot of air or gas. From the farther end of the cylinder are two tubes, one of which runs into the narcotizing chamber at the lower part, the other to the long tube in the Wolff's bottle below the surface of the narcotic fluid within the bottle. From the short or escape tube from the bottle is a continuous tube, terminating over the cage containing the animal. By an extra tap coal-gas can, if desired, be let into this chamber.

The animal to be slept into death is placed, resting on a little straw or hay, in a cage, which is then dropped into the large receptacle, the lid of which is at once closed. The handle of the piston is then moved up and down at a regular and quiet pace. As the piston is drawn out, the cylinder of the pump is filled with air from the large receptacle, and, as the piston is pushed back, it forces the air with which the cylinder has been filled through the narcotic fluid, a portion of which it raises into vapor and forces into the cage. Eight strokes of the piston charge one cubic foot of air with the narcotic vapor to saturation, and, as there are only nine cubic feet in all to charge, a couple of minutes are sufficient to charge throughout.

The animals in this apparatus pass quickly into sleep, and die not quite so quickly, but quite as painlessly, as in the larger structure.

This smaller apparatus will be so complete when it is finished that it may be wheeled from the station to a private house, if that be wanted; or it may be used in the streets for giving painless death to wounded animals. It may also, in future, be constructed at so comparatively trifling a cost that I see no reason why every town in the country may not be in possession of one, and every small animal be spirited away in sleep. Compared with other modes of extinguishing animal life—such as hanging, drowning, poisoning by prussic acid, shooting, stunning—the lethal method stands far ahead on every ground of practical readiness, certainty, humanity.

By means of carbonic oxide, sheep can be put to sleep with the greatest rapidity before they are slaughtered. I have submitted forty sheep in this way to painless death, and found that no bad effect whatever is produced in the flesh unfitting it for food. The objection to retention of blood, so strongly felt by the Jewish people, does not obtain, the animals in the narcotic state yielding up blood just as freely as in the ordinary way, when no narcotic is used. The same process is equally applicable to swine, calves, and fowls. To oxen I do not as yet see its immediate application.

It is believed that the larger apparatus could be constructed now for from £150 to £175, and the smaller for £50.

The cost of charcoal for the stoves with the addition of anæsthetic fluid is, in the large chamber, a little over one halfpenny per animal when eighty to a hundred are killed at one time. When fewer are killed the expense is a little increased; the trouble and substance required being as little for a hundred as for a less part of that number.

  1. Abstract from "Journal of the Society of Arts."