In the course of this work we have frequently insisted on the fact that we are being continually poisoned during the processes of life, either by poisons coming from without into our body through food or drink, or by toxic substances being formed in our body through defective metabolism. We have a series of glands with internal secretions which have properties antagonistic to these poisons, the most important of such glands being the thyroid, parathyroid glands, adrenals and the liver, which act by destroying these injurious products.
The following can now happen: Either these toxic products may be produced in such enormous quantities that even the increased functions of these glands will be insufficient to overcome them, or the glands may not be in a condition of complete integrity. In either of these cases the bulk of these poisons will be carried to the eliminating organs to be dealt with, viz.: the skin, the intestines, and the kidneys.
As we shall see, the skin alone is not able to eliminate more than a certain portion of these products, even by the additional assistance of perspiration. In addition to the skin the intestines may also assist the work of the kidneys, by expelling principally the poisons from the digestive organs. But only a small portion of the poison circulating in the blood will be eliminated in this way, especially if there is a lazy action of these organs. Thus the great bulk of all these products is carried to the kidneys, which are, indeed, our most important organs for the elimination of toxic products from the blood.
It is furthermore important to consider the kidneys because they are also glands with internal secretion. This is evident from the fact that uræmia is a condition which is dependent upon the absence of such a secretion.[220] It is not caused only by the retention of urine and the urea contained therein, for cases have been noted where there has been no urine for as long a time as seven days, and yet there was no uræmia, whereas uræmia rapidly develops at times in spite of an abundant flow of urine and elimination of urea. Thus, logically, uræmia must be ascribed to another factor, which can only be the absence of an internal secretion from the kidneys, which may otherwise perfectly perform their work. Another convincing proof of this statement is the fact that we are able to treat with great effect, as we have personally observed, diseased kidneys with extracts from the kidneys of pigs. We will demonstrate the action of this in a separate chapter.
That the kidneys are glands with internal secretion has been proved already by Brown-Séquard,[221] Meyer,[222] and other authors, among whom we will mention as two of the last authorities on this question, Professor Senator and Professor Hermann Strauss.
The kidneys, being glands with internal secretion, must then stand in close relation to the other ductless glands, according to the law established by us in our previous works. As already mentioned, we have shown in a communication to the Paris Biological Society, February 25, 1907, that these glands have an intimate relation to the thyroid gland, and vice versâ. Thus, alterations of the thyroid always produce changes in the condition of the kidneys. These alterations in the kidneys may, however, not necessarily be based on the intimate relations between thyroid and kidneys as ductless glands, but may be produced by the fact that, when the thyroid is degenerated and cannot destroy toxic products, these poisonous matters will be thrown on the kidneys (the skin and intestines not being of assistance under such conditions) and eliminated by them. Naturally the passage of such poisonous products through the kidneys is liable to produce changes in them, and albuminuria and hyaline or granular casts may show themselves in consequence.
The same may also happen after changes in the liver. When this important organ is not able to destroy poisons they are carried in increased quantities to the kidneys, whence their passage will produce albuminuria and hyaline and granular casts, as has been especially described by such French authorities as Huchard, Teissier of Lyons, Molière and Gouget, etc., as occurring in diseases of both liver and gall-ducts.
The appearance of albuminuria, and even of hyaline casts, must be taken as a proof of an abnormal condition of the kidneys, and this notwithstanding numerous authorities who are inclined to regard such an occurrence in a more lenient way. We hold, with Professor Senator, that the permanent presence of such elements in the urine is the proof of the fact that the kidneys are not in a normal condition. Even the orthostatic albuminuria of quite healthy persons, which, as its name implies, only occurs when such persons have been standing for a time in an upright position, has been considered by Senator as an expression of the existence of certain changes in the kidneys. According to Senator, the hyaline casts also are not such an innocuous symptom as certain authorities claim, but they are formed from the degeneration of the convoluted tubules. This is the most important element of the kidneys, for the greater part of the solids and toxins are excreted by its cells from the blood, and besides this function these epithelial cells also have an internal secretion. The appearance, therefore, of hyaline casts (which, as Senator found, could be proved under the microscope as having been formed through degeneration of the epithelial cells) must be considered as evidence of the loss of the secreting portion of the kidneys and of the destruction of their most important elements, and can be found regularly in all the toxic processes that take place in the body, showing that the poisonous products of these processes have passed through the kidneys and been eliminated.
Thus we find albuminuria and casts, and even signs of a serious inflammation of the kidneys, in different infectious diseases, and even after tonsillitis; also after other toxic conditions caused by the secretion of toxic products in the body from certain ductless glands, such as the sexual glands during puberty and the thyroid gland in Graves’s disease. Likewise in certain diseases where waste products of metabolism cause uric acid to be formed in large quantities, as also in diabetes, where a quantity of other toxic products, besides uric acid, are produced.
From the foregoing it is only natural to expect that different toxic products which are introduced into the organism from without, either in the food or in the drink, or which result from the decomposition of meat and alcohol and other stimulants, will also, for the most part, be eliminated by the kidneys, especially with a dilatory performance of the other disintoxicating organs. When passing in large quantities, or sometimes even in smaller numbers, they may be able to irritate the fine epithelia of the tabula epithelia and also those of the glomeruli, and produce casts (hyaline ones especially) and albuminuria. After large quantities of alcohol such a condition can even become permanent if the other toxin-secreting organs are sluggish.
In his experiments on animals Penzoldt has produced albuminuria by means of English mustard, pepper, and particularly radishes, and still more so after black tea. Gunzburg noted this also in a boy of 13, and Roth in a child of 3½, in both cases after the use of black tea.
Albuminuria and casts can frequently be observed after the administration of drugs in degrees varying according to the toxicity of the drugs. We have published a case in which even epithelial cells of the kidneys, single and in casts, as well as blood-casts in quantities, have been found after an administration of chloride of potassium. Luttje found casts in 33 cases out of 207, and in 92 of these albuminuria, after the administration of salicylates, and he issues a warning against their continual usage. That the same occurrence has also been observed after the use of other poisonous drugs such as mercury, chloroform, etc., will only appear to us as natural.
The skin and intestines, which co-operate continually with the kidneys, are able to do a part of the work of the latter by eliminating poisons which otherwise would have been carried to the kidneys, injuring the delicate structures by which they are secreted and through which they pass. As will be found in the chapter on the functions of the skin, this tissue is able to eliminate (especially when its functions are increased, as in cases of perspiration) a part of the harmful products, among them being some of the nitrogenous end-products of metabolism, and also common salt. But when the skin is unclean and its pores are clogged by dirt and the products of perspiration, and when it is diseased, as in skin diseases, or when it is burnt extensively and the sudorific glands destroyed, then these poisonous products are directed to the kidneys, whose secreting structure will naturally be injured by their passage.
The same may also happen after an obstruction or hindrance to the intestinal functions. When the passage of fæcal matter is retarded for a long time, a re-absorption of toxic matters can take place by the blood, necessitating their elimination by the kidneys, with harmful consequences to these important organs. This has been proved by experiments made by Wallerstein, who mechanically closed the anus of rabbits and dogs. After but twenty-four hours he found albuminuria and different kinds of casts in the rabbits’, and casts only in the dogs’ urine. It is very important evidence in favor of our supposition that the convoluted tubules of the kidneys play the most important part in the excretion of harmful products from the blood, that Wallerstein found, after four days, that the greatest change had occurred in the convoluted tubules of the kidneys in these animals. The epithelial cells of these tubules were greatly degenerated and in a state of coagulation necrosis.
Similarly English[223] has found albuminuria and casts in cases of strangulated hernia in men, in consequence of the stagnation of the contents of the intestines and the re-absorption of toxic matters. Similar results may also occur according to Leichtenstein, Senator, Jaffé, etc., in cases of intussusception, incarceration, and similar pathological conditions.
Thus we can all easily understand how the stagnation of the intestinal contents, as, for instance, in chronic habitual constipation, may also be injurious to the kidneys; and, indeed, Kobler and Huler have described albuminuria as a consequence of constipation. Not only is the elimination of excrementitious substances checked, but there is re-absorption of poisonous products from the intestinal contents which the kidneys must excrete.
That poisonous products coming from the intestinal tube are apt to produce even serious changes in the kidneys has been proved by Heller and Fishel after catarrhs of the stomach and intestines. At the same time we will also mention that in cases of intestinal auto-intoxication we can also observe a diminution in the quantity of urine, as noted by several authors, of whom we specially mention Boas and Hemmeter.[224]
From the foregoing there can be no doubt that most of the toxic products in the blood are eliminated by the kidneys. This is also the manner in which the nitrogenous end-products of metabolism leave the body. The kidneys act as a kind of filter for these products. When the kidneys, however, are changed or degenerated by the formation of connective tissue and loss of the elements of excretion, as in old age, then these products will be retained in a greater or smaller number, and a condition of auto-intoxication follows, to which we have previously ascribed a great rôle in the pathology of old age. Logically, if we wish to prevent old age coming on too soon, or a diminution of our chances for a long life, we must do our best to prevent such a diseased condition.