plants, of minuter animals, and of ferments and processes which produce cattle-plague, cholera, and many diseases. This is not mere fancy. We know already that mould will grow out of them, but can we always find its germs? This must surely be because we cannot distinguish in an early stage one kind from another.

We have spoken of antiseptic bodies that crumple up organic matter, and cause it to lose one of its most characteristic qualities, putrescibility. When we apply antiseptics to these minute bodies in the air, the result will be the same as on a larger scale to giant growths. This then is the whole explanation of fumigants; they mix with the air, enter into every corner of a room, and attack every atom floating free, treating it as it would a piece of meat, which we know may be preserved for ages. Disinfection by fumigation cannot then be said to be supported by a mere theory, it is an action as certain as salting meat, but more effective, because we can use agents more powerful than salt. We have here the explanation of all the strivings of those men who have used vinegar, camphor, and perfumes, aloes, myrrh, and cassia, as well as chlorine, muriatic, sulphurous, and carbolic acids.

The truest antiseptics are volatile organic bodies. They do not destroy, they preserve. They prevent action; and how delicate are the gradations of this influence! If we inhale ether we lose one of the most characterizing portions of animal life-the relation to an external world. We lose sensation; at a later stage we lose the action of mind. If we take alcohol, we have the oxidation disturbed, and the power of exertion, whilst less carbonic acid is given out. This is at least so in many cases, as Dr. Edward Smith has shown. But when we use carbolic acid as a strong liquid, we have the chemical action of the muscular fibre itself stopt. We can occasionally observe numerous stations between these points. These agents produce in succession anæsthesia, drunkenness, and destruction of the motion of life, ending in the suppression even of those movements needful for decay. We have proposed to treat the agents of disease existing in the air exactly as the Egyptians treated their dead, by the use of antiseptics, and unquestionably, if organisms infect the air, they will die in the presence of these agents as animals or vegetables die, and be preserved as mummies are preserved, until washed into the soil. But if any one is afraid that the disease is only allayed by these means to burst out again, let him remove the disinfectants from the mummies, and he might almost as soon expect them to return to life.

Metals, Oils, etc.-Metals for fumigation have not been mentioned. It has often been said that Birmingham has been

extremely free from cholera, and the possibility of metallic exhalation filling the atmosphere has entered men's minds. It is not impossible. In a place where copper is being soldered, we may smell it readily; where lead or zinc is melted, it may be seen as a white oxide on the walls. The neighbourhood of chemical works has always been considered remarkably free from infectious disease, and around St. Rollox in Glasgow, one of the largest in the country, this was remarked, and especially by the workmen themselves. These men sometimes discover things that the better informed quite miss; they have no theories. They come with bronchitis to a chemical work, and bring their children to the sulphur-burners to be cured of hooping-cough, and discover for themselves the disinfecting powers of chlorine, muriatic acid, sulphur, and metals; admiring the wonders of nature without caring to infect the world with their knowledge. They are like tender feelers put out by society. Scientific men ought to take up their slightest fancy, and bring it up into a thought which will in many cases be highly true and valuable.

We have remained long with these volatile disinfectants, but there are many others- so many that the world may wonder at infection existing. What shall we say of the powerful pepper, the pleasant lavender, the admired pennyroyal, and rue? These, and many others, have their value, and we use them when there is little or no danger, just as in our country-places we do not use the stronger bolts, but merely shut the door, as in the daytime, to keep out the wind and the cold. We have not studied the peculiar nature of such a substance as fusel oil, powerful in disinfection, and also in its action on animals, and, like carbolic acid and cresylic acid, to be brought in as an alcohol, making the whole series of the alcohols remarkable in this respect. How many other alcohols and ethers may be found capable of acting on the mind and the senses in various other ways, for our good or our evil, it is the business of chemists to inquire. If those to be found have influence on human thought, action, and suffering even, although very much less than those already discovered, the world may be much changed.

Amongst the volatile disinfectants we include a great number of oils. It may not be desirable to trouble the reader with exact tables, so we shall give rather hurriedly the general results obtained by experiments on the following bodies.

When meat is exposed to the vapour rising from phosphorus, it is rapidly decomposed, and resolved into inorganic salts.

When exposed to the vapour of cresylic and carbolic acid, kreosote, aniline, fusel oil, oil of mustard, and oil of bitter almonds, it does not, in months, become putrid, although with aniline and bitter almonds it becomes unpleasant to the sight and smell.

The others cause it to retain its form, and seem to arrest change, exactly as freezing would do. Now, we suppose that they will act on the poisons in the atmosphere exactly in the same way. Some persons argue that as they do not destroy, they are of no value, but we do not care to break them to atoms or to reduce them to their elements; we are quite satisfied if they are killed and unfit for mischief.

The same persons tell us that chlorine kills, and therefore is more valuable. It kills, but in killing it dies. On the other hand, tar acids remain long, and are active during the whole period, never being destroyed. Again, we cannot use chlorine except under cover. We may use the tar acids in yards and even in fields. If we pour them on the ground even in a very dilute state, they give off their odours, and may be perceived at a distance of hundreds of yards. They disinfect the ground and the air at the same time. We cannot do this with chlorine, nitrous gas, muriatic acid, or sulphur.

Meat treated with the vapours of naphthaline, Canadian petroleum, turpentine, camphor, oil of cinnamon, Bergamot, pepper, thyme, orange peel, lemons, valerian, aniseed, and asafoetida, became putrid in a couple of days after the flesh by itself had given way.

Meat treated with nitro-benzole, oil of cumin, hops, rosemary, juniper, and peppermint, became bad six days later than the above.

Meat treated with vapour of coal naphtha became slimy and disagreeable, but not putrid.

The same treated with wood naphtha, kept for a long time fresh, but became like that treated with oil of mustard, very white. Treated with oil of rue a very unpleasant putrescent appearance was observed, but no smell of putrefaction.

Butyric ether kept the meat fresh about eleven days longer than the air.

Heavy oil of tar, peroxide of hydrogen, and McDougall's powder, did not give out vapour sufficient to preserve meat. Carbonic acid did not preserve it, neither did protoxide of nitrogen.

We may say, in few words, substances which preserve organized matter from change are antiseptics, those which destroy the products of putrefaction are disinfectants. But distinctions which are not very practical are often thrown aside, and the classification is not yet valuable.

Charcoal, etc.-If the substances to be disinfected are in the air, it is useless to employ solid bodies-gases and vapours only can reach them. We might, it is true, filter the air entirely, say through charcoal, as Dr. Stenhouse proposes, and into our rooms

or cow-houses allow no breath to enter that had not been purified. The charcoal, especially if platinized, would extract all the poisonous substances; but who is to cage us up? This process is possible only in hospitals, and even there the difficulties are numerous. That substance, charcoal, is now used as a purifier of sewer gases, which afford it a wider field for its activities; the gases which leave the sewer pass first through it, and enter the air free from odour and danger. The plan adopted at the Houses of Parliament could also be used, and a fine spray, as first employed by Mr. Gurney, could be formed in the passage through which the air was carried, thus effectually washing and rendering it as pure as a Scotch mist does the atmosphere before it presents it to the shepherd. Instead of water, permanganate of potash could be used for spray, and besides the washing, we could have the oxidation, as Mr. Condy, we believe, proposes. Or instead of that we could use peroxide of hydrogen for the spray, and send oxygen into the room in a highly active state, and this is probably the best mode of obtaining an increase of vital air, if such were desirable. Where spray was not formed, the peroxide could evaporate quietly from a basin, and do its work of its own accord.

There are, however, other agents for washing air, but the mechanism of washing is an objection; we can never be sure that every floating particle is reached. Some persons will strew the ground with charcoal; the air will be absorbed and purified when it comes to the charcoal, but when it does not come there can be no action upon it. The same observation applies to all liquids and solids: they are valueless against an enemy which comes, like air, in invisible gas or vapour.1

We desire much to know the condition of the matter that poisons the air. We have concluded that it is a solid or a liquid, which may rise in vapour, as in miasms. But miasms do not infect, so far as we know.

Cattle-plague, perhaps, more than any, shows an indifference to season, and flourishes in heat and considerable cold, in dryness and moisture. It is propagated both with and without contact. We think that to consider it as a solid brings the clearest explanation. What kind of solid? Is it a vegetable

1 Speaking of mechanical modes of treating the air, we may mention a respirator by Mr. John White, surgeon, Finchley. In using this the air passes through a number of threads moistened with water, and, in fact, becomes washed. We cannot doubt that by this mode impurities will be removed from the air. The same vessel may be used to contain volatile ingredients according to requirement. Mr. W. has also ingeniously adapted the same idea for the use of sheep and cattle.

or an animal particle? Perhaps when it is found nestling in the flesh or the blood of our cattle, it will be difficult to tell its paternity. Cholera, on the other hand, waits for warm weather; its vitality begins, we are inclined to think, at 54° or 55° F., the temperature of decomposition, and of the incipient feeling of freedom from cold in men. If cholera poison were a liquid, warmth would not tend to concentrate, but rather to evaporate it; but if it were a solid in a state of decomposition, or a solid in solution existing as a drop, the cold would prevent its action. If, however, this arrived at a warm spot, might it not develop? Occasionally we do hear of cases in cold weather. If the poisonous particles pass through the air, they seem to be chilled by it, as dormice are put to sleep, and perhaps never recover their activity except in the case of one in millions. In some such way we must account for their movements; but our chief object at present is to destroy them. We cannot give rules better than those given; the fumigants mentioned kill organized things, and if poisons are organic, they must be set at rest under the treatment.

There are two cases in which disinfection is needful:

First, when the air is tainted by causes not in our control, as during pestilence.

Second, when the air is tainted by causes under our control, as the want of cleanliness and accumulation of manure.

In the first case we use gaseous disinfectants, of which we have already spoken.

In the second, where cleanliness is not to be obtained, we use liquid or solid disinfectants.

In the first case we destroy the infection produced by nature in the air; in the second, we prevent the infection from passing into the air. Gases or vapours are used for the first cases, liquids or solids for the second.

DISINFECTION OF SOLIDS AND LIQUIDS.-This brings us to the second part of the subject, for which we have left too little room. We have spoken of matter conveyed by the winds, of matter the existence of which in the air many will deny, although we have sources of it at our doors, which hundreds of carts employed by day and night are scarcely able to remove, -a heap of rubbish that continually follows man, and compels him to decency or an early death, whilst he has never understood the problem of its removal in its fulness, and has been too contented, even after Æsop laughed at him, to crow from his own midden. We have cities with a centre of filth and also of disease for every five people, and men wonder why they are ill. We have persons who tell us that we have sulphur