The chemico-vital theory is a combination of the two above mentioned. According to this belief the acids act upon the inorganic tissues; the irritation is conveyed to the pulp, which reacts against the invasion of the disease by throwing out lime salts into the fibrils.

The parasitic theory. The enamel being removed by acids, the organisms penetrate the tubuli of the dentine and proliferate there, according to some writers, merely expanding the tubuli for the better penetration of acids, and, according to others, generating themselves an acid by their action upon the organic matter.

The chemico-parasitic theory. This gives to acids the first place, to their agency all decalcification is due. Following this process come the micro-organisms, which penetrate only when decalcification is sufficient to permit their advance. Then they are found in great numbers, and cause the putrefaction of the organic mass.

The chemico-putrefective theory is the same as the above, save that the micro-organisms are only incidental to the putrefactive process, and have no part in the disease. Messrs. Underwood and Milles describe the microscopical appearance of carious dentine as follows:

"The tubes are filled with micro-organisms. They appear to penetrate the canals at first in single file, and then accumulate in vast numbers to encroach upon the matrix. Here and there a narrow line of bacteria or micrococci penetrate beyond the sphere of visible decay. Besides the disintegrated tissues and foreign particles, there is found abundance of leptothrix buccalis.

"The micro-organisms consists of micrococci, rodshaped and oval bacteria, and short bacilli.

"The number of sections of carious teeth cut and examined is now so enormous, that observers feel justified in assuming that the presence of micro-organisms is indispensable to the process "-(Sewill). Acids are necessary for the primary decalcifications.

The sources of these acids may be referred to the pro

cesses of fermentation and putrefaction, which are continually going on in the mouth.

Fermentation requires the presence of a ferment, which may be either organized, that is, living, or unorganized. Living ferments grow and multiply at the expense of the matters in which they occur. Yeast may be cited as an example of the former, and ptyalin of the latter. Moulds, yeasts, and bacteria, are all met with in the mouth. They gain access to it from without (Ziegler).

The mucous secretion and the secretion from the salivary glands combine to form mixed saliva. All starchy or saccharine substances taken into the mouth are converted into grape sugar by ptyalin.

Grape sugar, when acted upon by a yeast, the torula, undergoes alcoholic fermentation; the presence of the bacterium aceti induces acetous fermentation. Stomatitis and caries of the teeth have been observed to be especially frequent in the case of chronic drunkards, and it is probable that beer drinkers suffer more from these affections than those who indulge in liquors possessing a larger percentage of alcohol. May not the acetous fermentation of the liquor imbibed cause these conditions? Another yeast, the mycoderma vini, transforms the alcoholic products of the first torula fermentation into acetic acid.*

Milk is taken as food, acted upon by the bacterium lactis, lactic acid is produced.

Putrefaction also requires the presence of a ferment, and we know that the bacterium termo is that ferment(Ziegler). Naegleli, Pasteur, Lister, and others regard puctive fermentation as the direct result of the vegetation of the bacteria. Bacteria, as they grow and multiply, withdraw from the nutrient liquid the elements they require

*Naegleli maintains that the torula and the myco-derma are not distinct species, and, according to Grawitz, the white patches, known as thrush, are due to the presence of the myco-derma, the mycelial filaments and spores of which are distinguished as belonging to the Oidium Albicans. (Ziegler).

for building up their cells. These are chiefly C. H. O. N. from carbohydrates and albuminoids. The necessary inorganic compounds are derived from salts containing sulphur, phosphorous, magnesium, and potassium. None of the

bacteria can develop without water-(Ziegler).

When albuminoids undergo decomposition, we have formed formic, acetic, butyric, valerianic, caproic, and lactic acids; combined with ammonia, or other organic alkalies, leucin and tyrosin, sulphuretted hydrogen, carbolic acid, and various other substances. When proteïds are entirely decomposed, there remains a substance rich in fats, in earthy and ammoniacal salts, phosphates, and nitrates. (Rutherford).

In hyperæmia of the mucous membrane, there is an excessive secretion of mucus. The chief constituent of mucus is mucin, an albuminoid substance, ready splitting into a number of simpler bodies. Animal substances are taken as food into the mouth. These are principally composed of albuminoids and fats. One of the products of their decomposition is lactose, which breaks up into lactic acid.

We may say, then, that putrefactive fermentation may be set up by the action of bacteria on the mucous secretion, either alone or along with remains of food. When the mucus is extremely viscid, it may determine the location of caries by causing the adhesion of food, &c., to particular surfaces.

In the two processes of fermentation and putrefaction, two acids-acetic and lactic-are formed. These both act powerfully on the teeth.

According to Leber and Rottenstein's experiments, a solution of acetic acid of the strength of 1 in 1000 decalci fied in 17 days the enamel and adjacent dentine of a tooth placed in it; a 10 per cent. solution of lactic acid showed during the same time, a very decided action on another tooth. It is probable, then, that acetic and lactic acids, along with other acids, produced in the putrefactive decom

position of albuminoids, dissolve the lime-salts of the dental tissues.

*

Miller, of Berlin, states that micro-organisms are never to be found in any but decalcified tissues of the tooth, and this is probable, as bacteria cannot live without water, and it is difficult to believe that they can go on in advance without it. We may, therefore, conclude that they await decalcification. When the dentine is reached, channels are hollowed out to admit the fluid collecting in the cavity behind. In this.float the organisms, deriving nourishment partly from it and partly from the disintegration of the organic matrix, by this means producing, and setting free, the acids of putrefactive fermentation to continue the process indefinitely.

The exclusion of water, as a means of stopping the invasion of caries, has long been recognized, and the energies of successive generations of dentists have been devoted to the application of water-tight fillings.

We may conclude, then, that the secretion of the mucous membrane takes part in certain fermentative and putrefactive processes, when in sufficient quantity, either alone or in combination with saliva or foods. That micro-organisms superinduce putrefactive decompositions of albumin

*Drs. Leber and Rottenstein, who, in 1877 78, published their researches on the origin of caries through the action of leptothrix buccalis, differ from Miller.

There is, they say, no manner of doubt that the elementary parts of the fungus penetrate into the interior of the canals, and there develop in a manner to acquire a relatively considerable diameter.

It also results from the very fact of the dilatation of the canals, that the appearance of the fungus is not accidental, and, that it is not by a purely passive action that it invaded the canals. It is necessary that there be a proliferation of spores infinitely minute and innumerable of the fungus to effect the dilatation of the tubules. It is, moreover, very important that the elements of the leptothrix should have, at a certain stage, a mobility of their own, in virtue of which they easily penetrate the interior canals. As for the rest, we have met in the canals with only the granular masses of the leptothrix, and never the filaments which appear to show themselves only at the surface. [The granular masses are probably only the disintegrated tissues.-E A. C.]

oids; that such processes produce acids which act by decalcifying the dental tissues, and so make way for the microorganisms found by Miller and others. That these organisms, by removing certain constituents of the organic matrix of the dentine, produce putrefaction, and consequent disintegration. That the locality of caries may be determined by the collection of organic matter on dental surfaces, coated with viscous mucous.

The section on pathology has been largely taken from Ziegler's Pathological Anatomy. I have also referred to the following works :-Salter-Dental Pathology and Surgery. Harris-Principles and Practice of Dentistry. Wedl -The Pathology of the Teeth. Tomes-Dental Surgery. Tomes-Dental Anatomy.-Odonto-Chirurgical Society of Scotland.-London Dental Record.

ARTICLE II.

PROBABLE OR POSSIBLE POISONING FROM DENTISTS' AMALGAMS.

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BY A PHYSICIAN.

(Read before the Mississippi Valley Society)

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Sometimes the deluded victims prefer to be poisoned. Sometimes they dread the dire effects of the deleterious article, yet seem to be led on, as if by siren songs, to fatal results. At other times they seem indifferent, possibly through ignorance, but oftener because the injurious results are slow in progress and not violent in their manifestations. Even when the bad influences are liable to be transmitted from generation to generation the indifference remains. Posterity poisoned? What has posterity done for us?

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Well, who cares?

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