But there are cogent reasons for not accepting the view that the acid is the cause of the rheumatism. For if it were so, the rheuma tic symptoms should persist so long as the acid existed in adequate excess in the system, and should decline when it ceased to do so, and not till then. Remedies, too, which neutralize the acid should also. cure the rheumatism ; while those which did not do so should fail to have any curative effect. The early advocates of the lactic-acid theory believed that the administration of alkalies, by neutralizing the acid, would cure the rheumatism. And theoretically such should have been the case. But the reality has been very different. For though, in the absence of any better mode of treatment, alkalies continued to be for many years the chief remedies administered in rheumatism, we very well know that they exercise little or no control over the disease. They may be given so as to saturate the system, and ren der the urine alkaline, without doing good to the rheumatism. The disease seems to last as long, and to run the same course when treated by alkalies, as it does when it receives no treatment at all. If the acid caused the rheumatism this should not be.
Again, we find that salicin and salicylic acid cure acute rheuma tism effectually and speedily—as will be evidenced further ou. It is impossible that their curative effect can be due to any neutralizing action on lactic acid. Their effect is produced also independently of any action on the eliminating organs. It is certain that these reme dies neither neutralize nor get rid of the acid, for in cases of acute rheumatism which are thus cured the perspiration often continues to give an acid reaction for four, six, or more days after fever, pain, swelling, and all symptoms of rheumatism, except this acidity, have disappeared. This continued acidity of the perspiration so long after the rheumatic symptoms have ceased is no doubt due to the presence and excretion of acid formed during the continuance of the disease. It has an important bearing on its pathology.
It indicates, first, that the acid in the system is neither neutralized nor destroyed by the remedy which neutralizes the action of the rheumatic poison, arrests the rheumatic process, and puts an end to the disease.
Secondly, it shows that the mere presence of lactic acid in the system does not necessarily give rise to rheumatic symptoms.
Thirdly, it indicates that it is the production of the acid in excess, not its mere presence in excess, which is essentially associated with these symptoms. In other words, these symptoms and the presence of lactic acid in the system would seem to be associated together as conjoint results of the rheumatic process. Ou this view of the matter excess of lactic acid in the system becomes one of the ordinary symptoms of acute rheumatism—a result and not the cause of the morbid process which constitutes the disease.
2. The injection of lactic acid into the systems of the lower animals has been said to be followed by inflammatory chanyes similar to those which occur in acute rheumatism.
Many years ago Sir Benjamin Ward Richardson published an account of some experiments made on cats and dogs, by injecting lactic acid into their peritoneal cavities. The results of these experi ments he regarded as favorable to the lactic-acid theory of rheuma tism; and they have been referred to by various authors as one of the reasons for accepting that theory.
A careful perusal of Dr. Richardson's paper would seem to indi cate that there have been accorded to his experiments a wider scope and greater significance than are their due. For in none of the ani mals experimented on was there induced a morbid condition which we would call rheumatism in man. What Dr. Richardson found, and all that he found, was that in animals into whose system lactic acid had been injected, there was observed, after death, redness of a por tion of the endocardium. Endocarditis, and not rheumatism, seemed to be the malady induced. But as endocarditis is frequent, and an excess of lactic acid invariable, in acute rheumatism, the inference was drawn that these experiments demonstrated the accuracy of the view that lactic acid is the morbid agency which gives rise, not only to endocarditis, but also to the rheumatism with which endocarditis is usually associated. The inference is wider than the facts warrant.
Moreover, a careful examination of these facts indicates very im portant points of difference between the condition noted by Richard son and that which occurs in connection with acute rheumatism—so important, that we are led to regard the results of his experiments as negative, so far as the pathology of acute rheumatism is concerned, and the inferences drawn from them as inadmissible.
What Dr. Richardson teaches is that in both induced and rhen taatic endocarditis the cause of the inflammation is lactic acid in the blood, and that the acid produces its effect by a direct irritant action on the free surface of the endocardimn.
The bearing of his experiments on our subject may be considered under the following propositions, taken from Dr. Richardson's paper, and given in his own words : 1. "In rheumatic endocarditis the poison is produced in the pul monary and destroyed in the systemic circulation." 2. "Lactic acid could not exist in the blood without producing endocardial mischief." 3. " The action of the poison which produces the disease (rheu matic endocarditis) is directly on the free surface of the endocardial membrane; the poison acts, in a word, after the manner of a local irritant." (a) The first proposition is a most important one—so important that it cannot be accepted without evidence; for on its accuracy de pends the validity of Dr. Richardson's whole argument.