When we review all these dietary regulations, that in great part have been developed from practical experience, we will discover that they are all based on the same principle and all emanate from the same idea, namely, to save the diseased organ, the kidneys, as much as possible. Protective therapy in general is intended in the first place to save the diseased organ all superfluous work, and in the second place to eliminate all those irritants from the diet that might stimulate it to increased effort. Such treatment is particularly rational in nephritis, because the functional powers of the kidneys in this disease are reduced to such an extent that in order to perform any additional work at all the last vestige of reserve force would have to be expended. F. A. Hoffmann, in a series of brilliant writings, was the first to undertake an analysis of the principles governing this method of treating organic lesions of certain organs. For a long time we have been in the habit of treating certain organic and functional diseases of the nervous system, certain disorders of the stomach and intestine and, in particular, certain heart lesions by this method, and in many instances we may be gratified to find that protective treatment produces marked improvement in the functional powers of the affected organ or even restores approximately normal functional activity in cases in which the organ was damaged by irreparable anatomic lesions. We must always remember, however, that protective therapy directed toward sparing one organ should never go so far as to indirectly damage some other important organ, or the organism in general. This caution seems to be so self-evident that it seems hardly worthy of particular mention; nevertheless, unfortunately, it is frequently neglected : we often find that a certain dietary or other prescriptions are given that may be perfectly rational as far as the disease of one organ is concerned, but that unquestionably do harm to the organism in general. In other words, dietary regulations are frequently one-sided, and consequently injurious. Some ten years ago I undertook to study this question in detail, particularly in regard to the routine treatment of diseases of the stomach in vogue at that time. I am much gratified to find that this little monograph acquired some significance in the subsequent development of the dietetic treatment of diseases of the stomach.

We will see below that in the treatment of diseases of the kidney the ordinary routine prescriptions may occasionally do harm, and actually have been followed by deleterious consequences.

There are certain natural limits to every system of protective therapy. In diseases of the heart, for instance, we cannot reduce the activity of the organ below a certain level; in diseases of the stomach we cannot reduce the functional activity of the stomach beyond a certain degree; and the same applies to the kidneys, for, in the case of these organs, we can only reduce their excretory function to a certain extent. In estimating to what extent we are justified in sparing the organ, we must remember that in acute diseases of the kidneys we can and must carry the protective principle further, and may at the same time expect more rapid and better results than in chronic forms of nephritis. We know this from our general pathologic experience, and we know from clinical experience, besides, that if we do not treat acute forms by sparing the organ, this neglect is fraught with more serious results than in chronic disorders. In diseases of the heart, the nerves, the stomach, etc., we proceed in exactly the same manner and (as we see from the short sketch of the ordinary method of treatment that I have given in a preceding chapter) the same principle is now established in the treatment of acute and chronic diseases of the kidneys.

The question arises, How are we to know whether or not this or that diet really spares the kidneys ? In the first place, we must study the results of general clinical experience, and must attempt to determine how the general course of the disease is modified by one or the other system of dietary regulations. I consider this study of the development of the disease to be by far the most important criterion for the administration of any given diet. This question can, in fact, only be an swered on the basis of clinical experience; we must presuppose, however, that the person who attempts to answer this question has really enjoyed a particularly wide experience in regard to the influence of different forms of diet on the course of the disease. In this particular field it is rare to encounter such individuals, for many clinicians who talk and write on the dietetic treatment of diseases of the kidneys are so prejudiced in favor of the common method of treatment that they have employed no other therapy for years, consequently they are by no means qualified to judge whether some other system of therapy might not produce better, or at least equally good, results. I will have occasion to show later on that my own extended experience is in many respects at variance with commonly accepted views.

A second important criterion is the degree of albuminuria, particularly if the absolute quantity of albumin voided in the urine in twenty-four hours is determined, and we do not content ourselves with estimating the percentage of albumin in the daily urine by analyzing a few samples that are voided at random. This is a very important point, and has been emphasized by different authors; unfortunately, it is not sufficiently considered in practice. It is, of course, altogether wrong to consider albuminuria an index of the severity of the disease, particularly in comparing different cases of nephritis with one another. A patient with contracted kidney, for instance, may excrete 0.1 per cent. of albumin in the urine, and may at the same time be in less serious condition than another case with contracted kidney who is only excreting 0.02 per cent. of albumin. But, even in estimating the gravity of any individual case, albuminuria should be utilized with great care as an index of the intensity of the disease at any given period and as an indication of the good or bad results of any particular method of treatment. Only in the case of acute nephritis do I consider albuminuria to be an important and, under certain circumstances, a conclusive index; for here there can be no doubt that, as a rule, improvement is accompanied with a decrease of albuminuria, whereas an exacerbation always goes hand in hand with an increased excretion of albumin.