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. Footnote 223: Oesterr. Med. Jahrbuch, No. 2, 1884. 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.