Again, pericarditis is almost as frequent as endocarditis in acute rheumatism. The two are due to the same cause, and produced in the same way ; hut Dr. Richardson leaves pericarditis out of account altogether, and gives of the occurrence of inflammation of the mem Irane which lines the interior of the heart, an explanation which cannot apply to inflammation of that which invests it externally.
For these various reasons, we regard the inferences which have been drawn from Dr. Richardson's experiments as fallacious and un warranted; and the experiments themselves as affording no valid support to the lactic-acid theory of rheumatism. The results of ex periments made on the lower animals may readily have their impor tance exaggerated; and we cannot exercise too great caution in draw ing from them inferences applicable to man. Though certain effects are got from the administration of this and that drug to a cat or dog, it by no means follows that like results would follow its administra tion to man. This objection is peculiarly applicable to Dr. Richard son's experiments. There are abundant observations to show that the only invariable result of the administration of lactic acid to man is increased action of the skin. But this is a result which could not be got in dogs, for they do not perspire.
But above and beyond all these very cogent reasons for rejecting Dr. Richardson's teaching these is another one even more potent. It has been demonstrated by Reyher that the enclocardial signs which Dr. Richardson attributed to the action of lactic acid are found in all dogs, no matter how they are killed. Richardson, and Rauch who supported him, omitted to satisfy themselves before making their experiments as to what was the normal appearance of the endo cardinal in the clog after death. Had they done so they would have found it to be exactly that which they described as morbid, and as the result of the action of lactic acid on it. The redness which Richardson regarded as pathological, and as the result of the direct irritant action of the lactic acid, has been shown to be the normal condition of the lining membrane of the right side of the heart of the dog, no matter how death is brought about.
3. The administration of lactic acid to man has been followed by symptoms of acute rheumatism.
Since Cantani recommended lactic acid as a remedy in diabetes, numerous cases of that disease have been thus treated. In several the administration of the acid has been followed by symptoms indis tinguishable from those of rheumatisin, pain, and swelling of joints, with rise of temperature.
One of the most remarkable is a case related by Dr. B. Foster in which there occurred six well-marked arthritic attacks : "The phe nomena corresponded in all respects to those which are characteristic of acute articular rheumatism. They came on when the acid was taken, and ceased when it was discontinued. When moderate quan tities of the acid were tolerated, an increase in the dose was succeeded by the painful inflammation of the joints. Coinciding with the de velopment of the articular affection was the appearance of perspira tion, at first only slight, but afterward, in the more severe attacks, copious and acid. These facts," continued Dr. Foster, " have dis pelled the last lingering doubt in my mind as to the truth of the lactic-acid theory of rheumatism." One cannot read the details of Dr. Foster's cases without feeling that we have in their facts strong evidence in support of the lactic acid theory—to my mind, the strongest that has been adduced in its favor. Such evidence cannot be disregarded or ignored; either we must explain it, or our refutation of the lactic-acid theory must re main imperfect and inadequate. Can it be explained? I think it can; and that even Dr. Foster may be shaken in his renewed alle giance to his old love.
Lactic acid is a product of tissue metabolism—an excretory product therefore. Such products when retained unduly in the system exer cise two distinct actions—first, a stimulant action on the organ by which they are normally eliminated, and second, a disturbing action on the tissues which supply the materials from which they are formed. The retention, for instance, of an excess of carbonic acid in the sys tem causes, first, increased force and frequency of respiration, and ultimately paralysis of that function and asphyxia. Excess of urea in the blood causes, first, increased action of the kidneys, and ulti mately that condition of tissue asphyxiation to which we apply the term mTemia. So with lactic acid, its retention in the system causes, first, increased action of the organ by which it and its products are normally eliminated, and second, functional disturbance of the tex tures during whose retrograde metamorphosis it is formed, if for any reason the eliminating organ failed in its duty.