acetate of lead and sulphate of zinc were placed in the same dose. The physician was probably well aware of the fact that each salt is an active astringent, but he had probably altogether forgotten that sulphate of lead is insoluble, and that therefore there would be double decomposition and recombination, resulting in sulphate of lead and acetate of zinc. The latter of these is an astringent, while the other is inert, hence either one of the original salts would have given him as good results as he gained from both.

Sometimes we may be fully aware of the tendency to change, through affinity, yet not able to control the changes so that the desired one of those possible may take place. As an illustration, we have in sulphur a substance in itself nearly inert, but some of its posible combinations are very active. In some cases of general prostration, as through blood-poisoning, this substance would be the best medicine possible, perhaps, could we but control the direction of its affinity. Let it combine with oxygen to the degree necessary to produce sulphurous acid, and we have a very active disinfectant, antiseptic, alterative, and anti-alkaline, if the word can be tolerated. It is well known that sulphurous acid, and also the sulphites, which are the compounds it forms with alkalies and alkaloids, are able to prevent and ordinarily to arrest fermentation and the preliminary steps towards putrefaction. In the visitation of Asiatic cholera in 1849, we used sulphur in many cases, and very often with apparently good results. We learned to rely on it more when ozone was found plentiful in the atmosphere; and it may be possible that the greater proportion of active oxygen tended to its oxidation rather than to the formation of other compounds.

Let the sulphur undergo oxidation to either the first or the second degree, thus being converted into sulphurous, or to sul huric acid, and the possible influences are not difficult to calculate. Consider the former. It may be dissolved in the gastric fluids, either free or combined, and carried into the circulation. In itself it is an antiferment; but in the route it readily finds materials with which it may combine. Alkalies, alkaloids or alkaline carbonates may meet with it, and combination ensue. Suppose it finds carbonate of potash or soda, the base is taken, and a sulphite is formed, while carbonic acid is set free. And it is not necessary to delay to remind the reader that the system is always ready to take care of a little carbonic acid in the general circulation. The sulphite thus formed is itself an anti-ferment, and thus, and otherwise not necessary to mention, it is a blood purifier.

Changed to the second degree, or sulphuric acid, the results are not very much different, one leading difference, however, being found in the fact that the sulphates are not anti-ferments to the extent that the sulphites are.

Now in very many cases, in the practice of general surgery, and also in the specialty of dental surgery, the general or constitutional action is not very desirable. But how to obtain this action to an efficient degree is a suggestion more readily made than answered. One would think that the sulphurous acids of the shops might be readily obtained and easily administered. But the acid of the shops is simply an aqueous solution of the acid in its quiescent condition. When copper or a similar metal decomposes the sulphuric acid of commerce, sulphurous acid rises as gas bubbles. These, as they escape may be collected and condensed in water, thus giving the watery solution of the acid. But this solution does not meet the wants nor fulfill the indications of surgical science, general or special. The trouble is that the acid when thus prepared and ready for use is passive, while we want it active.

But however desirable it may be to have it oxidized when sulphur is administered as a medicine, let us suppose it takes a course entirely different and unites with hydrogen, and we have an acid to be sure, but in the form of a very offensive, stinking gas, that is very easily decomposed. This gas is often, if not generally, called sulphuretted hydrogen, and it is a principal cause of the bad odor of a rotten egg.

Acting locally on the mucous membrane of the intestinal canal, it causes uneasiness and often severe pain. Acting on the terminal nerve loops, it often causes spasmodic contraction of the bowels, causing a sensation like colic, if not actually producing the disease. This acid, too, is soluble, to some extent, in the gastro-intestinal fluids, and may be taken into the general circulation; and if there, it must act as a deadly poison. Its sulphur will take iron from the red corpuscles, which renders the iron wholly unable to longer carry the oxygan necessary to give force for organic life. Not only is there the strong affinity of iron and sulphur for each other to induce this change, but the oxygen found in the blood may take the hydrogen of the poison, to form water, thus liberating sulphur in its active condition. But the sulphide. of iron can perform no useful function in the blood, and therefore the function of the red corpuscles is destroyed to the extent of the changes thus occurring.

Before this, and often indeed, we have alluded to the two conditions of oxygen, the active and passive, sometimes called the nascent and the quiescent. This allotropic fact may be demonstrated in many ways. Even though the affinity of oxygen and hydrogen is the strongest known to chemistry, other things being equal, these gases may be kept together indefinitely without combination. The common explanation is that the gaseous state is unfavorable to combination, because the particles are so far separated as to be beyond the range of affinity. But by passing an electric spark through the mixture combination instantly takes place. And why? Some say that on the principle of electric attraction and repulsion the particles are pressed together; but this does not seem satisfactory. Is it not more natural to conclude that the gases are changed from the passive to the active state by the electric force? As stated elsewhere, iron may be kept in oxygen indefinitely without oxidation or rusting, but an eleciric spark passed through the oxygen so changes it that the iron is rapidly (To be continued.)

corroded.

Painless Dentistry.

Humanity dreads pain, and unfortunately many operations about dentistry are painful or disagreeable. Much of the pain and inconvenience of dental operations may be saved the patient if the dentist is considerate and careful. Too often dentists forget they are operating on living organs supplied with those telegraphic pain reporters-the nerves-and work much as the carpenter does on the board he is cutting. Sometimes it is necessary and pain is unavoidable, but it can be alleviated or entirely prevented by the use of the many remedies-nerve obtunders-for destroying pain. Other things being equal, the dentist who is careful and considerate of the comfort of his patients will find he is appreciated. He may lose time, but he gains in other ways. But there are people who are uselessly nervous and who act very foolishly on visiting a dental office. These things combined have had the effect to absolutely frighten many a timid person from ever having anything done for the teeth. This is all wrong. When people properly appreciate the value of good teeth and the evil effects of bad ones, they will better appreciate the value of dental services and the necessity of giving the best care to the saving of the teeth: Still, there is fortune and fame awaiting the person who shall produce a painless method in dentistry.-Health and Home.

Dr. Jacob. L. Williams thus writes in the Jour. American Med. Asso., 1885:

"In the early part of my professional pupilage I heard a suggestion from the venerable John C. Warren, long since deceased, to this effect. He said: "When engaged in a long surgical operation of half an hour or more in duration, the eyes will sometimes become fatigued, and it will be difficult and unsafe to continue the operation with them in that condition. It is better under such circumstances to raise the eyes and let them rest upon some object in a distant part of the room, or, if you can leave the operation, step to the window and look out for a minute or two; you will then return with the eyes refreshed, and can see as well as ever." And more recently one of the most eminent American oculists has written that "one great cause of the injury to vision is the application of the eyes to book or work after they have become fatigued." This mention is made because the ideas therein contained represent a principle which holds good in the use of any faculty.

There is a very common belief that mere "exercise strenth

ens, without the recognition of any other element as necessary to that end. And so some seem to think that the more and longer they can exert their faculties the stronger they must be. As a result we see fatigue carried to exhaustion, which is another name for weakening and debility.

Instances are common in various occupations and ages of individuals. The youth is too often crowded with study continuously through the day, and perhaps part of the night, until the mental process becomes actually debilitated, sometimes permanently. The business or professional man will not or cannot pause for rest till he finds that he positively must, and sometimes not then, but drops at his post. The ambitious rower or pedestrian continues his exercise till his strength is absolutely gone, and sometimes his constitution shattered.

This rule then should be learned, and the earlier the better, namely, to rest, if possible, just when we are tired, and to let our patients do the same."

DENTAL SOCIETIES.

ILLINOIS STATE DENTAL SOCIETY.

The Twenty-Second Annual Meeting will be held at Rock Island, Ill., beginning Tuesday, May 11, 1886, and continuing four days.

Dentists in this and adjoining States are cordially invited to

attend.

J. W. WASSAL, Secretary,

208 Dearborn Avenue,

Chicago.

PENNSYLVANIA COLLEGE OF DENTAL SURGERY.

The Thirtieth Annual Commencement of the Pennsylvania College of Dental Surgery was held at the American Academy of Music, Philadelphia, on Saturday, February 27th, 1886, at 8 P. M.

The address to the graduates was delivered by Albert P. Brubaker, M.D., D.D.S.

The number of the students of the session was one hundred and forty-six.