Popular Science Monthly/Volume 41/May 1892/Bad Air and Bad Health II
|BAD AIR AND BAD HEALTH.|
EXERCISE, as well as pure air, helps us in our constant struggle against the poisons that we manufacture within ourselves. It does this by driving the blood charged with oxygen, by means of the pressure of the muscles called into play, more thoroughly through the tissue (Foster, page 219); and thus it would quicken the breaking down of dead tissue into its safe and final waste products (water, carbonic acid, and urea), and shorten the period during which the dead tissue was passing through various dangerous forms which it temporarily assumes. From this fact we may infer that the man of sedentary life, above all others, requires pure air.
In truth, pure air and exercise are equal forces acting in the same direction. They both get rid of waste, and with it of the poisons in the system, which are depressing various organs. We need not, therefore, be surprised when we are told by Sir D. Galton that after barracks were better ventilated the rations of the men had to be increased; or by "the pathetic story" of certain seamstresses whose work-room was ventilated, and who then begged that the old state of things might be restored, as their appetites had increased beyond their earnings. Sir D. Galton gives another experience, illustrating the depressive effect of these poisons upon the functions of life. A New York medical man rather cruelly shut up some flies without food, some in foul air, others in pure air; the pure air being constantly changed. To his surprise, the flies in the pure air died first, these dying from simple starvation; while the flies in the foul air died from poison, and with the tissue of their bodies unexhausted, indicating how the functions of life were carried on to the last where oxygen was available, but had been slowed and depressed by the presence of the poison, so that life was actually maintained longer in the foul than in the pure air. To take one more example. Parkes tells us (page 159) that it was found in the case of miners that they required six thousand cubits of air introduced per man per hour (this included the air necessary for horses and lights) to be able to work at their best. When this quantity was reduced to one third or one half, there was a great reduction in their working energy. In other words, the poison within their system being imperfectly oxidized, impaired their faculties.
We could wish that it were possible to write the whole of the noble story of oxygen from a physiological point of view. It is a double service that it performs for us. It not only, as we have seen, neutralizes the deadly poisons resulting from waste, but it provides the heat and energy, by the oxidizing or burning up of this waste. All through animal life the consumption of oxygen, serving this double purpose, is the measure of activity. Just as reptiles and cold-blooded creatures consume small amounts of oxygen and develop little activity, so birds and insects consume immense quantities of oxygen and develop immense activity. Each animal has, as Prof. Foster believes (page 812), its own peculiar quantity, its coefficient, so to speak, of oxygen, which it consumes—an amount which, judging from the few instances he gives, seems to vary with intelligence; thus the dog consumes more than the rabbit per pound of its weight, and a man more than a dog. In the same way, a waking man consumes more oxygen than a sleeping man, a man at work than a sedentary man, a young man than an old man, a young child more than the young man. The restless activity of children marks both their great consumption of oxygen and their pressing need for it by being allowed to breathe abundance of pure air. Rapid and extensive waste is going on in every child's body. Tissue of every kind, including bone, is being constantly broken down in order that it may be built up anew on a larger scale, and it is therefore the greatest cruelty in their case not to provide them in fullest measure with the purest air. Unhappily, very little thought is given to this matter; and with quite young children whose need is the greatest of all our nurseries are only too often mere slaughter-houses. Mothers of all classes should try to see the meaning of the fact that out of four deaths of infants one takes place from lung collapse, a state that often follows bronchial inflammation (see R. D. Powell, Lungs; Quain, page 861), and probably of ten indicates the source of the mischief. Dr. Douglas Powell significantly says, "All causes that interfere with respiratory efficiency favor the occurrence of the condition named."
It is now right for us to look at the subject of these waste poisons in special reference to the skin. Without referring here to the different calculations made on this subject, it is enough to say that much less carbonic acid escapes from the skin than from the lungs; more water (if we are to follow Prof. Foster who differs from other authorities, who again differ among themselves we may say roughly, 1·5 pound from lungs, and 2·5 pounds from the skin per day), and a larger amount of solid matter The solid matter is put at one or two per cent of the whole 2·5 pounds and two thirds of this one or two per cent is organic matter containing the poisons in question. We can see the importance of the skin, as an organ of excretion, in various ways. In the first place, the provision of an enormous number of sweat-glands under the skin, supposed by Krause (Baker's Kirk, page 427) to be between two and three millions in number in the parts where they are least abundant they are over four hundred to the square inch offers evidence of a physiological character on the point, even if, as is stated, some small part of skin perspiration takes place independently of these glands. Then we have the evidence of the disagreeable odor from the skin and clothes where cleanliness is not observed; again, we have the curious facts of death having both actually and nearly occurred in cases where the body has been covered (the mouth having been left free) with gold-leaf or plaster of Paris. Various explanations have been given, but Prof. Foster seems to think (page 697) that the retention of poisonous matters "constituents of sweat, or the products of some abnormal metabolism" (change) which would have been discharged through the sweat-glands, is largely concerned in the matter. We venture to believe quite independently of certain experiments that this conclusion can not be avoided.
We have also a most remarkable case recorded by Sir D. Galton. Some men in the horse artillery had left their bedding rolled up for two months, without its being opened to the air. When first used again, man after man who had slept on this bedding came into hospital with "a suspicious fever." It would be difficult to find a case that more vividly illustrates both the poisonous character of the emanations of the body and the necessity of free ventilation in order to render them harmless. Again, when serious consequences result from a chill owing to the constriction of the blood-vessels of the skin and interference with the sweatglands such as a dangerous affection of the kidneys (Richardson, page 283), or a congestion of the spleen (Richardson, page 307), or the inflammation of bone and periosteum (Richardson, page 323), it seems probable that the cause of mischief in all these cases is either the retention of normal poisons that ought to have escaped through the skin, or the formation of abnormal poisons during the inaction of the skin. [We think it is Dr. Richardson who makes this suggestion.] Again, the fetid exhalations from lungs and skin in starvation seem to show that the breaking down of tissue, which is very rapid in these cases, is resulting in a larger discharge than usual, through skin and lungs, of putrescent matter.
From what has been already said, we ought not to feel surprised that those who live in foul air are not only lowering their health, but are carefully preparing themselves both for lung and bronchial affections, and for such diseases as scarlet fever, typhoid, small-pox, dipththeria, dysentery, cholera, etc. As regards cholera, we extract the following interesting account given by Dr. Carpenter. He states (page 360) that in the fatal autumn of 1849 there was at Taunton an exceedingly badly ventilated workhouse. In the school-rooms there were only sixty-eight cubic feet or less per head. The fatality of the cholera attack thus carefully prepared for—was awful. Within forty-eight hours after the first attack, nineteen deaths and forty-two seizures had taken place. In the course of a week sixty, or twenty-two per cent of the whole number, died, almost all the others suffering badly. Fewer boys died as compared with girls, because, as it was stated, having even less air than the girls, they used to break the windows. In the jail of the same town, where each prisoner had over 800, and in some cases over 900 cubic feet, and where a system of ventilation kept renewing the air, there was not "the slightest indication of the epidemic influence." In August, 1849, the cholera raged severely in London, the mortality having increased from nearly 1 per 1,000 in June and July to 4½ in August and September. It happened that at this moment a large number of male prisoners were transferred from Millbank Prison—which was in one of the bad districts—to another part of the country, the numbers being thus reduced from over 1,000 to close upon 400; while at the same time the female prisoners were slightly increased in number in Millbank Prison, from 120 to 131. The consequences were remarkable. The mortality of the female prisoners went up from a little over eight to a little over fifty-four per cent (which was considerably above the rate of increase in the outside districts), while the mortality of the men fell from slightly over 23 per 1,000 to nearly 10 (the June and July rate of mortality). Carpenter gives other interesting examples, and also remarks upon the fact that the special centers of cholera existed before the invasion of that disease as fever nests; and that cholera followed the footsteps of other diseases, not only in the same district, but in the same streets and houses, and even rooms.
As with cholera, so with other causes of death. At Secunderabad, in India, in old days, the barrack accommodation for the line was example as regards troops; but the worst of all was to be found in the Indian jails, where, in some instances, 70 cubic feet only of air was the average allowed; in no cases did it exceed 300 cubic feet. The mortality was, as might be expected, one in four. It was a humble imitation of the Black Hole of Calcutta. So at the end of the last century, in the Dublin Lying-in Hospital, the mortality from trismus of the children was one in every six born; by better conditions of ventilation, it was reduced to one in nineteen and a half (Carpenter, page 985); and this number of deaths was again reduced. So in the London workhouses of the last century, twenty-three out of twenty-four children died in their first year. By reforms, especially by improved ventilation, the number of deaths was reduced from between 2,000 and 3,000 to between 400 and 500 (Carpenter, page 365). So with our soldiers. When barracks improved, especially in the matter of ventilation, deaths from zymotic diseases fell from 4·1 per 1,000 to 0·96 per 1,000 (Galton). So in the case of our sailors on board the Kattlesnake, a case which came under the notice of Prof. Huxley. The crew (Carpenter, page 256) had acquired by confinement (this seems to have been the special cause, though not the only cause) a predisposition to disease. No malady appeared, however, until one of them slightly wounded his hand: then typhoid resulted, and ran through the whole ship's company. They had carefully prepared themselves for disease with the poisons of impure air.deficient, and the average annual mortality of the men was nearly double the average of the presidency. At the same station, both the officers, who were well quartered, and the detachment of artillery, who had roomier barracks "at no great distance," did not share in the heightened mortality (Carpenter, page 363). Barrackpore furnished an even worse
We suspect that no class of human beings suffers so much from the poison of foul air as infants. Older children and grownup persons are seldom so much shut up, and the diseases by which so many infants die, infantile diarrhoea, convulsions, and infantile pneumonia, strongly suggest the irritation likely to be produced by breathing these waste-poisons; though improper food must also bear a large share of the blame. Of all the evil consequences, however, of foul air none can be traced more surely than phthisis or pulmonary consumption. Wherever men are crowded together without care and proper means to supply them with fresh air, there pulmonary disease shows itself. Parkes, Dr. A. Ransome, Sir D. Galton, and others have collected many interesting examples bearing on this matter. Sir D. Galton tells us (page 502) that after our barracks were improved ventilation being one of the leading improvements chest and tubercular disease, which had been fatal to 101 per 1,000 soldiers, was only fatal to 4·2, and in the same way that, with proper ventilation (and other improvements) of the stables of the horses, coughs and catarrhs disappeared. He also quotes Dr. Leeds, of New York, to show that the supposed cure of sending a consumptive patient to a cow-stable was in reality the cure of sending him into somewhat purer air than that of his own room (page 502). Dr. Richardson quotes a case where no less than nine members of a family following the occupation of Cheap Jack were in succession the victims of consumption from sleeping in a traveling van, their life in the open air during the day being insufficient to counteract the poison breathed in the night (Our Homes, page 11). Parkes also tells us (page 152) that in the royal navy and in the mercantile navy bad ventilation and phthisis, occasionally amounting to a veritable epidemic, have accompanied each other; and he quotes many authorities insisting upon the close relation between foul air and pulmonary consumption. On the same point—the slaughter produced by unventilated barracks—Dr. Richardson tells us the mortality in the army before Sebastopol was during twenty-two weeks ending May 31, 1856, at the rate of 12·5 per 1,000 as against 20·4 of the Guards quartered in England (Our Homes, page 13). Dr. A. Ransome reports (Health Lectures, 1875-76, page 149) a case as late as 1861, where fearful lung disease broke out in some of the ships of the royal navy. The arrangements were actually such that only fourteen inches space was allowed to each hammock, and the air above the hammock was 8 to 10 hotter than below.
The same evidence comes from the sedentary trades, some of which "afford experimental conditions for the development of disease"; from the cases of phthisis, or destructive lung disease, among cows in unventilated sheds (Parkes, page 162); from the higher rate of consumption in town as against village, and city as against town (Hirsch, page 213)—in each case the dearer lodging implying more overcrowding; from the outdoor treatments now recommended for consumptive patients; and from other sources.
When we come to pneumonia, it is still the same poisons, we believe, which indirectly are at work. As in pulmonary consumption the bacillus finds its food prepared for it in the unhealthy state of the blood and tissues altered by the poisons that have been rebreathed from foul air so also must it be in pneumonia; if we are to accept the statements made about the bacterium of pneumonia (Crookshank, page 273). Secondary pneumonia, which is a lung attack resulting from the poison in the system from such a fever as typhoid, throws some light upon this matter, and seems exactly to explain the origin of ordinary pneumonia. In ordinary pneumonia we believe that it would be found that the person attacked had been living in rooms where the air was tainted, had breathed consequently, again and again, the exhaled poisons, until these poisons had so altered the tissue as to allow the bacterium to form its lodgment; in other words, that he was as much "poisoned" as the person suffering from secondary pneumonia. Of course a slight chill, by arresting the action of the skin and thus increasing the poison in the system, is likely enough to be the immediate precursor of the attack by rendering the conditions still more favorable for the germ. Again, latent pneumonia in quite young children is sometimes masked (Quain, page 880) by the signs of the nervous disorder which precedes it. This nervous disorder tells the story. It is caused by the poisons which are acting on the system, and which at last produce the attack of pneumonia.
It might, however, be urged that a person leading a healthy outdoor life might, after severe exposure, be attacked by pneumonia. Certainly, and in his case the attack would mean poisoning (that is, predisposing for the germ by poisoning) through the skin; just as in the case of the man living in bad air it would mean poisoning through the air taken into the lungs.
Now, granting that this is a true explanation, that pneumonia, or even common cold, is a case of poisoning, and only a case of cold in a secondary sense, it is worth noticing that the effect of these poisons must be felt in the throat and bronchial passages and lungs much more than in other organs. These poisons would cling to the sides of the throat and bronchial (and nasal) passages, and would often enter the lungs. In the case of persons living in foul air, these organs, being more exposed and in intimate contact with the poison, would probably be saturated with it, and therefore would be always prepared for disease. We can then understand at once why the leading symptoms of a cold are violent flow from the nose, sneezing, coughing, with the accumulation of phlegm, and painful soreness in the throat. These symptoms "become intelligible at once from the point of view of local poisoning, and we see in all the circumstances of a cold the "protective efforts" which Nature makes to eject the poison—of whatever kind it may be—from the parts which are specially attacked, just as we often see in diarrhœa the effort to get rid of an irritant, or in fever, with its rapid disintegration of tissue, of the poison that has attacked the system. Of course, as in pneumonia, some slight chill often immediately precedes the attack of cold—the chill, by its arrest of skin action, throwing more poison into the blood, which is sufficient to determine the attack in the predisposed part.
We believe, therefore, that few healthy persons would be subject to cold, unless they lived in impure air. With an old person, or a person in lowered health, it is different. A defective machinery for the circulation of the blood or for respiration might readily result in the waste-poisons being imperfectly separated from the blood, and thus such persons would live in the same state of blood-poisoning and preparation for attack as a young and healthy person does who constantly breathes bad air. Where we have cases of liver or kidney attack following upon a severe chill, we may suppose either that the poisons retained (or formed) near the surface of the body pass into the blood, and then act through the nervous centers upon those organs which happen to be specially susceptible; or that the poisons, imperfectly breathed out at the lungs, are carried directly to those organs.
We wish that it were possible to follow the subject further, but we have already overstepped the limits which the kindness of the editor has allowed. We can only say, in conclusion, that we are convinced that very grave issues are dependent upon the question of pure air in our houses. We suspect that not only liability to cold, but to gout, rheumatism, lumbago, neuralgia, some forms of headache, and many forms of nervous irritation are to be conquered by constantly giving lungs and skin a fair chance of getting rid of these poisons; we feel sure that the irritable temper that so often accompanies severe literary work, and at last ends in the "break down," must largely be put to the account of the impure air breathed through long hours; and we suspect that much of the intemperate drinking in towns results from the depressed feeling which follows work done under similar conditions. We think a great society should be formed to arouse the interest of all classes in this subject, and that inquiries should be made the answers being published as to the provision for fresh air existing in hotels, concert-rooms, theatres, schools, churches, etc. We are, both of us, opposed to action being taken through state inspectors. The present evil will never be really overcome until individual interest is aroused; and the state inspector does not develop individual interest. We shall be glad to communicate with any persons anxious to take steps in the matter, and shall hope to draw up a short! paper containing a few practical suggestions of a simple nature. Meanwhile, without discussing systems of artificial ventilation, we say to everybody: "Live as much as you can with open windows, wearing whatever extra clothes are necessary. In this way you will turn the hours of your work to physical profit instead of to physical loss. If you can not bear an open window, even with an extra coat, and a rug over your knees, when you are sitting in a room, do the next best thing, which is, to throw the windows wide open not a poor six inches whenever you leave it, and thus get rid of the taint of the many dead bodies that we have breathed out from ourselves, and that hang like ghosts about our rooms. Smuts, as we confess, may be bad, but they are white as snow compared with impure air. Pay special attention to the constant exposure to pure air both of clothes and of bedding. Avoid chill, that is one form of poisoning. Avoid impure air, that is another and much more insidious form of poisoning."
Our present addresses are: Harold Wager, Yorkshire College, Leeds; and Auberon Herbert, Larichban, Cladich, Argyllshire.
Several gentlemen have been kind enough to read the foregoing paper, and to express the following opinions upon it. Sir Lyon Playfair writes:
Prof. Huxley writes:
Furthermore, it is highly probable that the decaying organic matter given off from the whole free surface of animal bodies, taken in conjunction with its microbial contents, is a source of danger, but whether directly or indirectly is a point about which I should not like to speak confidently.The fact is, while the virtues of fresh air and the wisdom of physical purity as a prophylactic may be very confidently justified by experience, the theory of the subject is full of difficulties, and the present views of physiologists must be regarded as merely tentative hypotheses. I should not feel justified in putting the theoretical points you advance as safely established truths before the public. I began to mark some paragraphs I thought specially open to objection; but I can not go into the matter, as I am myself struggling out of the influenza poison, which afflicts one's brain with mere muddiness.
Dr. Clifford Allbutt writes:
If any one doubt, let him try the marvelous recreation of a few nights camped out sub dio and be converted.
Moreover, the marvelous effects of an open-air life in the cure of such maladies as consumption are known of all men. But is it kind to tell us these dreadful things when we'are helpless to amend them?
Your home solution of the problem is known to your friends, and is excellent in your circumstances, but is impossible in towns, where every inch of window means an inch of grime on walls, ceilings, and furniture. Not only so, but our big common dwelling-halls are gone, our high-backed chairs and settles are gone, our tapestry is gone, and air supplied in modern fashion by slits or pipes means "drafts."
Now, "drafts" will kill some of us as quickly as ptomaines and far more painfully.Please write another paper to tell us what is to be done!
Dr. W. B. Cheadle writes:
The poor suffer from the small, ill -ventilated cubic space available for either sitting-rooms or bedrooms and the crowding of work-rooms; the better classes partly from the close offices in which some of them work, but chiefly from defective bedroom space and ventilation. Few people, I imagine, realize the fact that about one third of their whole lives is spent in their bedrooms, and that they pass this third part of their existence in an atmosphere so poisoned by organic matter that it would not be tolerated in a sitting-room for a moment. The amount of space allowed in bedrooms and dormitories is frequently altogether insufficient. Doors and windows are tightly closed, and there is practically little ventilation going on for six or eight hours of sleeping time, whereas in sitting-rooms the admission of air is promoted by persons passing in and out.
This steady nightly poisoning goes on in many public institutions, I am afraid, in the "houses" of some public schools, and the dormitories of charitable institutions. They are well ventilated during the day, closed at night, and the allowance of cubic space is quite insufficient to supply fresh air enough with the very small influx which can take place.
Night nurseries, again, especially in large towns, are liable to be grossly overcrowded. I have seen a small, low room in the attics of a London mansion used as a sleeping apartment for five or six children and a nurse which had not space or ventilation enough for two persons.Without indorsing the whole of the pathology suggested in your excellent paper, I am sure you are right in attributing a large proportion of ill health, contagious disease, and especially the increased virulence of this, to air fouled by organic matter.
Prof. W. H. Flower writes:
I am not sufficiently acquainted with modern physiology to know whether all the scientific details of the paper are correct, but I quite agree with you in the very great importance of the subject being pressed home upon all classes. How, for instance, could people travel in a railway carriage with perhaps six or more companions shut up together for several hours, and insisting on keeping all the windows closed, as they often do, if they were made to realize that the air which they are breathing must necessarily be passing in and out of the lungs, not only of themselves, but of all their fellow-travelers as well, over and over again in the course of the journey, and each time becoming more and more contaminated?
I have always thought, though I have not medical experience enough to prove it, that the greater prevalence of tuberculosis and other lung disease in cold over warm climates is owing, not so much to difference of temperature, as to the fact that in the former there is a greater tendency to breathe impure air for the purpose of warmth. My theories on the subject are, however, rather staggered by the thought of rabbits, sand-martin, etc., passing a considerable part of their lives at the bottom of burrows, where anything like ventilation seems absolutely impossible, and yet remaining perfectly healthy.
Mr. Lawson Tait writes:
What can I add to an article, so lucidly written, save that I agree generally with it, and hope that it may be productive of great good, as it well may?
Dr. Junker expresses, in the narrative of his travels in Africa, a somewhat favorable opinion of the intellectual qualities of the negroes among whom he traveled, and pronounces them capable of higher moral development. He everywhere found the upper classes, princes and nobles, the most highly endowed with intellectual qualities. This he attributes to the fact that the negro ruler is compelled to think and act in his capacity of judge, lawgiver, and captain. He notices, too, the wonderful fluency of speech acquired from the custom of making long orations, embellished with simile and metaphor, in their public assemblies.
- We may also take the case of races living in hot and cold climates. In hot climates we breathe a smaller quantity of oxygen (owing to the expansion of gases) than in cold climates. Thus, taking two climates, one of 32° F. and the other of 80° F., we should inhale about 2,164 grains of oxygen per hour in the one climate (the cold), and only 1,971 in the other climate (the warm), or a difference of about nine per cent (Galton, Our Homes, p. 498). This would in part account for the difference of energy that exists in the races of hot and cold climates; just as our own energy varies considerably on hot days and keen frosty days, though we think some allowance ought to be made for the more open-air life that would be led in the warm climate. The bearing of these facts upon crowded rooms should be perceived. As the room gets hotter, not only are we breathing more poison, but less oxygen, which is the only remedy for the poison. We are therefore doubling the causes of evil.
- So it has been stated. It is also interesting to quote the statement from the Registrar-General's Report for 1889, that there were in that year 71,056 deaths of male infants (not over twelve months) in England, and out of this number, 13,805 (roughly speaking, about one in five) died of diseases connected with the respiratory system. It is right to add that lung collapse may follow many different kinds of illness.
- Thus we should have from 118·3 to 236·6 grains of organic matter excreted by the skin in twenty-four hours.
- Of course it would be unfair to put all these cases simply and exclusively down to the effects of vitiated air, as we might, perhaps, in the case of the prison quoted above; since overcrowding in towns occurs among the poorest part of the people, living on the worst food, badly clothed, and therefore for these reasons exposed to attacks of disease; but with all such deductions the evidence is of a striking character. Dr. Richardson writes to the same effect. Speaking of relapsing fever, he says, "The disease (1847) followed where the habitation was most crowded" (Our Homes, p. V); and, again, "Certain it is that homes which are charged with impure atmosphere are the places in which septic diseases are most likely to be intensified and most likely to spread" (Our Homes, p. 21).
- These make up a very large proportion. See lectures by Sutton. Health Lectures, 1879-'80, p. 130.
- "Experiments have recently been made in Berlin, in a room closely shut up after the death of a consumptive patient. Six weeks after the death living microbes of phthisis were found on the mirror, walls, and picture-frames, and these introduced into the body of a guinea-pig produced the disease."—(L. P.)
- The violence of so-called Russian influenza in America is probably to some extent the result of the breathing of highly impure air, which is so common in that country. We suspect that this disease is just one of the many forms of trouble which appear where people live in constant disregard of the purity of the air of their living-rooms. The subject demands attention from this point of view.
- There are many interesting points—such as the discussion as regards the effect of dampness of soil, and Hirsch's theory as regards the high Mexican plateaus—which have to be considered, but they do not seem to shake the main fact that impure air is the great ally of pulmonary consumption.
- If on the other hand it is believed that pneumonia can arise without the intervention of the bacterium, we must regard it as a case of direct instead of indirect poisoning. That there is such direct poisoning we know from those attacks of the liver and kidneys which follow a severe chill, and throw back the poisons, which should have been excreted by the skin, on to those organs. Parkes (p. 164) strongly believed that bronchitic affections are often produced from the breathing of foul air. He does not, however, as far as we are aware, enter into explanations.
- The fact that the air that we breathe is delayed for some little time in the bronchia passages before reaching the lungs probably increases the local poisoning, and therefore the predisposition for attack by the germ of the parts when we breathe bad air. In this way perhaps the lungs are protected at the expense of the bronchial passages; and a cold is the violent occasional expurgation of those parts which are specially exposed to the poison.