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The Lactic - Acid Theory - Theories of Rheumatism

excess, system, acute, rheumatic, symptoms, skin and action

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THE LACTIC - ACID THEORY - THEORIES OF RHEUMATISM. Blood poisons may be divided into two classes : (a) Those which are produced within the system; and (b) those which enter it from without. The rheumatic poison is generally regarded as belonging to the former—as being some product of mal-assimilation, or imper fect tissue metamorphosis.

One of the characteristics of acute rheumatism is the occurrence of profuse acid perspirations. The urine too is hyperacid. This excessive acidity naturally led to the hypothesis that an acid condi tion of the blood had something to do with the production of the rheumatic symptoms. Dr. Prout made the definite suggestion that the materies morbi was lactic acid, and that the rheumatic symptoms resulted from the accumulation of this acid in the blood. This idea, enlarged upon and developed by Todd, Fuller, and others, was re garded by the profession as affording of the causation of acute rheumatism a more satisfactory explanation than any other hypothe sis hitherto advanced. It possessed, moreover, the advantage of affording a definite foundation for a rational line of treatment—the treatment by alkalies.

The lactic-acid theory was, for these reasons, very generally ac cepted, and for a long time was looked upon as quite satisfactory.

In time, however, the sufficiency of this theory began to be called in question, and doubts expressed as to the efficacy of the treatment by alkalies to which it naturally led. The failure of the alkaline treat ment indeed, more than any other cause, tended to bring discredit on the acid theory.

Lactic acid is a product of tissue metamorphosis. It is an un stable compound, which readily undergoes change, and is excreted by the lungs and skin as carbonic acid and water.

Its presence in excess in the system may be due to increased for mation, to defective elimination, or to a combination of these two agencies. The most perfect development of the lactic-acid theory is that which recognizes this combination.

Lactic acid is formed during the metabolic changes which take place in muscle. During exercise it is formed in larger quantity than during quiescence, and when the exercise ceases there is an excess of this acid in the system. But the exercise which causes increased formation of lactic acid is accompanied also by increased action of the lungs and of the skin, the channels by which the acid is elimi nated in the form of carbonic acid and water. Excessive formation

is thus counterbalanced by increased elimination, and no accumula tion takes place. But if, at this time, the action of the skin be checked, the metamorphosis and elimination of the lactic acid are arrested, it accumulates in the system, and the symptoms of acute rheumatism result. The action of the skin is checked by anything which chills the surface of the body.

Such is the most perfect development of the lactic-acid theory ; and such the manner in which this modern theory is combined with the old view as to the efficacy of a chill in the production of rheuma tism. The theory is ingenious and beautiful, and by no means de void of foundation. But it must not be accepted without a careful consideration of the evidence on which it rests.

The arguments adduced in support of this theory are the following : I. Acute rheumatism is accompanied by excess of lactic acid in the system ; the disease never occurs without such excess, and such excess is found only in connection with it.

2. The injection of lactic acid into the system of the lower ani mals has been said to be followed by inflammatory changes similar to those which occur in acute rheumatism.

3. The administration of lactic acid to man has been followed by symptoms indistinguishable from those of acute rheumatism. Let us consider each of these arguments.

I. Acute rite/emu/ism is accompanied by excess of lactic acid 'iv the system, and such excess is noted only in connection with if.

That no doubt is true ; and the accuracy of the statement is not called in question. The point at issue is the relationship which this excess of acid bears to the rheumatic process. Is lactic acid the rheumatic poison, and does its presence in excess in the system give rise to the phenomena of acute rheumatism ; or is the excess of lactic acid, like pain and fever, merely oue of the phenomena of the disease, one of the results of a morbid action set agoing by some other agency? According to the lactic-acid theory, the acid causes the rheuma tism. The main support of this theory is the fact which we are now considering, that there is always an excess of lactic acid in the system during the course of acute rheumatism.

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