I think we may notice, with regard to the lithates deposited in such circum stances, that those simply dependent on gastric derangement are of a paler color than those which are produced by any excess. To some it has appeared that the pink color was caused by chemical alteration of the same coloring matter which is secreted by the liver, and the staining of the utensil has been taken as evidence of biliary derangement ; the investigation of this point is not complete, but may be usefully remembered in practice.
Excess of urea is also one of the functional disturbances of the secretion. It is to be regarded as a proof of excessive metamor phosis of the nitrogenized elements, whether in consequence of a too abundant supply, or of unusual waste of tissue, as it follows on the use of nitrogenized food in excess, or is increased by dis ease. There is apparently no specific cause to which it can be attributed; we must be content at present to employ such general expressions as disorder of stomach and depressing influences, while observing the fact of general emaciation, sense of lassitude, and depression of mind which accompany its existence.
It is often associated with a deposit of oxalic acid, in the form of oxalate of lime. Probably too great stress has been laid on the presence of this salt, which has been often regarded as the first step in changes of which it is perhaps really the result; and this conclusion is the more probable from the very many and very varied circumstances in which it is found. It coexists with alkaline urine and deposits of phosphates, with acid mine and amorphous lithates, with crystals of uric acid, as well as with excess of urea: but we may always trace indications of weakness and depression, whatever other special characters the case exhi bits. We need not stop to inquire whether it be formed by a reconversion of some of the normal ingredients or by imperfect oxidation of carbon in the lungs, or whether it be formed at once in the process of assimilation, and carried into the urine as it is when food containing oxalic acid is taken into the stomach.
Many other functional disorders might be enumerated, but they are chiefly matters of curiosity; such, for example, as the presence of fibrin in chylous urine, of oily matter, of kiestine in the urine of pregnancy, of a milky albumi nous matter in malacosteon, &c. These cases are so rare that the student must be referred to works on diseases of the kidney for further information regarding them. It may be added that luematuria is to be regarded as a functional disorder when it depends only on some change in the condition of the blood, such as ill manifested in other parts of the body by spots of pur pure, or by uncontrollable hemorrhage.
The entire dependence of functipnal disorder on causes altogether beyond the kidney itself, is not less remarkable than the extensive associations of its diseases with those occurring in other organs. Among fevers we find scar latina giving rise to a form of nephritis with albuminuria : certain forms of chronic rheumatism and gout seem to be more or less dependent on degene ration of the kidney ; and the connection existing between gout and uric acid brings that disease into close relation with the crystalline deposit in the urine.
Dropsy is connected in two ways with disease of the kidney; as it is induced by deficient secretion of water, which thus necessarily accumulates in the sys tem, or by changes slowly developed in the blood rendering its watery portion more liable to transude through the vessels into surrounding tissues. The same condition gives rise at times to hemorrhages, especially epistaxis, and is always marked by the waxy or pallid hue of anemia. Tubercular phthisis often forms the conclusion of a case of diabetes ; chorea and delirium tremens are each said to cause important changes in the relative amounts of certain of the constituents of the urine.
Head affections are in a most especial manner associated with disease of the kidney : convulsions and coma are often the precursors of its fatal termi nation, whether caused by anemic poisoning, or by serous effusion in the ventricles. In a large proportion of cases of apoplexy granular degeneration is found, but the connection of the two is probably to be traced to disefse of the heart, which is so common in albuminuria. Occasionally this exists as simple hypertrophy ; at other times there is atheromatons disease of the valves, and perhaps of the arteries; the former apparently produced by dia. turbed circulation, the latter probably only another expression of that faulty nutrition which also affects the kidney.
Plastic exudations on serous surfaces are to be met with in the pericardium, in the pleura, and in the peritoneum more commonly than in other circum stances; and both bronchitis and laryngitis are more severe in consequence of the tendency to wdema to which it gives rise. The liver not uncommonly presents evidence of coincident disease, which it is not difficult to explain when we recognise habits of intemperance as the constant source of mischief to both organs.