In the former case the kidneys are at fault, and the difficulty arises from either organic or functional disease of these organs, usually the latter. It is probable, however, that the overaccumulation is more frequently due to overproduction than to deficient excretion. When this is the case it arises from one of two causes: first, deficient oxidation of a normal supply of ingested albuminoids; or, second, oxidation being normally active, it is still incapable of fully meeting the requirements of an occasional or habitual oversupply of peptones, and hence a quantity of only partially oxidized and very insoluble products is left in the circulating fluid to be with difficulty excreted.

This duty the kidneys will perform up to a certain point, and for a certain length of time; but at last, failing to be completely removed, they seek other channels of exit, chiefly the bowels, but in part also the skin.+ The bowels, being accustomed to the office of depuration, do not complain when any slight extra demand is made upon them; but the skin, less accustomed to the performance of this function, exhibits its impatience by pruritus and its rebellion by eruption.

If the supply of ingesta is normally and properly adapted to the body's needs, but oxidation is imperfect, we are compelled to seek deeper for a cause. It is to be found either in a deficient supply of oxygen in the blood, or, if the supply be hygienically sufficient, in a defective utilization of it.

This leads us to inquire how and where the general processes of oxidation are carried on in the body. Without stating the many theories which have been advanced in explanation of this process, I will simply offer the one which seems to me to have the greater probabilities in its favor, to wit, the one recently urged with so much force by Murchison.++ This writer believes that the liver is the principal seat of the oxidizing processes, and that deficient functional activity of this organ is the fons et origo of most of the troubles arising from suboxidation. I have the more readily accepted the views of Murchison, as deductions from a different set of data bad previously led me to suspect the liver of being intimately connected with the production of the Rheumic diathesis. It is also probable that a certain amount of oxidation occurs in the tissues, and even in the blood itself.

* Lectures on some of the Applications of Chemistry and Mechanics to Pathology and Therapeutics. London, 1867.

+ Gigot-Suard's Experiments (q. v.) seem to prove this. G. Bird (Urinary Deposits, has observed eczematous eruptions frosted with crystals of urate of soda. and I have myself obtained uric acid from the sweat of rheumic patients. Lactic acid has been found in it by others.

++ On Functional Derangements of the Liver. London, 1874.

Let us now return with the argument, and in the light of his theory trace a pound of beef from the mouth to the urinal. Entering the stomach it is acted upon by the gastric juice and changed into albuminose or peptones.* These are received by endosmosis into the portal capillaries, and are conveyed to the liver; here they wholly, or in part, undergo oxidation, and are conveyed thence by the hepatic vein to the vena cava, to the right heart, through the lungs, to the left heart, and from it to the general circulation, through the medium of which they are distributed to the tissues. Here, by further oxidation, perhaps, they become tissue, remain as such for a time, until, by still further oxidation, they are released from their morphological condition, and re-enter the circulation, perhaps as urea, perhaps only as substances capable, by still further oxidation, of becoming urea, and ready for removal by the kidneys. If, now, these normal precesses be anywhere obstructed, we have in the circulation the very insoluble products of deficient oxidation, which, unable to entirely escape by the kidneys, seek a vicarious exit, in part by the skin, and in so doing give rise to the cutaneous troubles we are considering.

What causes the tendency to deficient oxidation by the liver and other organs concerned? This is a question which we cannot definitely answer. Excluding cases characterized by a deficiency of red corpuscles, anaemia, chlorosis, etc., in which the proximate cause is very evident, we come to others, and by far the majority, concerning which we only know that sometimes the difficulty appears to be hereditary, and at other times acquired, and that in either case it is always difficult, and sometimes impossible to remedy, and that our efforts must be confined to controlling results rather than to eradicating their cause.

There is, however, another important change in the constitution of the blood, and one which results directly from this overaccumulation of suboxidized product. Uric, lactic, and oxalic acids, combining with the free alkalies or decomposing the alkaline carbonates in the serum, reduce its alkalinity - that is, render it subalkaline. Now, it is well known that processes of oxidation, whether within or without the body, are more readily accomplished in the presence than in the absence of an alkali; in other words, alkalies assist oxidation, and their diminished proportion in the blood-serum and the tissues greatly retards this normal process, + The importance of this fact, from a therapeutical point of view, will be immediately perceived.

This diathesis of suboxidation does not manifest its effects upon the skin alone, but also upon the mucous membranes and the joints; and. in all probability, underlies certain chronic organic lesions of the viscera. These, however, do not immediately concern us, and hence will not be specially referred to.

The third question which we are called upon to determine in connection with this diathesis is, the propriety of considering eczema, psoriasis, and pityriasis, among its dependents.

* I am considering simply the nitrogenous principles of the beef, not the fata, salts, etc.