"The muriatic acid may be shown to exist in the urine by the white curdy precipitate insoluble in nitric acid, which is formed, when the nitrate of silver is added to it, after the sulphuric and phosphoric acids have been removed by the nitrate of barytes or lead." pp. 20 and 21.
After finishing these introductory subjects, Dr. Prout proceeds to the consideration of the diseases of the urinary organs themselves; which he divides into functional, mechanical, and organic. Under functional diseases, we have first, those, in which principles soluble in the urine are morbidly deranged in quantity or quality, embracing three chapters; and secondly, those affections, in which principles insoluble in the urine are morbidly deranged in quantity or quality, comprising six additional chapters. Under the first subdivision, the first chapter is on the affections, characterized by albuminous urine; the second, on diseases, in which an excess of urea is the characteristic symptom; and the third, on diabetes.
The diseased derangement, consisting in an excess of urea in the urine, has not been particularly noticed by any writer before Dr. Prout, who believes that it has probably been confounded with that form of diabetes, called diabetes insipidus. The state of the urine and symptoms in this species of urinary derangement are thus described by our author:
"The average specific gravity of the urine seems to be a little above 1.020, and occasionally to vary from 1.015 to 1.030. Most generally it is pale, but occasionally it is high coloured, and exhibits somewhat the appearance of porter, more or less diluted with water; and this variety in appearance not unfrequently takes place in the urine of the same person. When first voided, it reddens litmus paper. For the most part, it is entirely free from sediment, except the mucous cloud of healthy urine; and the only remarkable property which it appears to possess, is that of containing abundance of urea; so that on the addition of nitric acid, crystallization speedily takes place. From the quantity of urea present, it is very prone to decomposition, and soon becomes alkaline, especially in warm weather.
"There is almost constantly in these diseases, a frequent and urgent desire of passing water both by night and day. This desire is for the most part evidently excited by actual diuresis, or the increased quantity of urine; but frequently it cannot be ascribed to this cause, as the quantity voided at one time is often by no means considerable; though in almost every instance that has fallen under my observation, the total quantity voided during any given time has appeared to be greater than natural. The quantity appears also to be particularly liable to be increased by cold weather, and by all causes producing mental agitation. There is sometimes a sense of weight or dull pain in the back, but this is by no means a constant symptom. There is also occasional irritation about the neck of the bladder, which sometimes extends along the urethra. The functions of the skin appear to be natural; at least in every case which has come under my own observation, perspiration has been rather easily induced. The pulse is not affected. There is no remarkable thirst, nor craving for food, except in extreme cases; nor are the functions of the stomach and bowels much deranged. Hence for the most part the tongue is clean, and the dejections regular and apparently natural.
"In most of the cases of this disease, which have hitherto fallen under my own immediate observation, the subjects have been middle-aged men, of thin and spare habit, with a sort of hollow-eyed anxiety of expression in their countenance, free from gout and constitutional disease in general, and, as far as could be ascertained, from any organic defect in the urinary organs. In every instance they had been induced to apply for medical advice, not so much from the pain, as from the inconvenience of the disease, and the dread of its ending in something worse; and, what may be worth remarking, in several instances confessed, that they had been addicted to masturbation from very early youth," p. 41, et seq.
The remedy for this morbid derangement in the urinary secretion, most successful in the hands of Dr. Prout, was opium, either administered alone, or in conjunction with alkaline medicines. It is rather a rare affection. When not arrested, it is liable, according to Dr. Prout, to pass into diabetes.
In his chapter on diabetes, our author makes many interesting remarks; but the space we are enabled to devote to this analysis, will permit us only to make an extract, which seems to prove a close connexion between the disease characterized by an excess of urea, and diabetes.
"It has been mentioned in the preceding pages, that an excess of urea frequently precedes the appearance of saccharine matter in the urine. Now it is a remarkable fact, that in diabetes, in proportion as the saccharine matter diminishes, that of urea generally increases; and in such instances, the presence of the former principle can not only be no longer distinguished by the sensible properties of the urine, but scarcely be demonstrated by the utmost skill of the most experienced chemist, though the specific gravity of the urine may at the same time be nearly 1.040. I have recently been favoured by Dr. Elliotson with the most complete and remarkable change of this description that has yet occurred to me. The patient, besides being diabetic, was in the last stage of phthisis, of which he died shortly afterwards. The quantity of urine passed daily, when I first examined it, was six or eight pints; its specific gravity was 1.038, and it contained a large proportion of very white sugar and very little urea. Dr. Elliotson under these circumstances gave opium, beginning with gr. i, and increasing the dose to gr. iii, thrice a day. The opium produced stupor, and was obliged to be discontinued; but the effects produced upon the urine by its means were most remarkable. In about 60 hours, the quantity of urine diminished to two pints, its specific gravity was reduced to 1.0174, the saccharine matter had apparently disappeared, and was superseded by urea, the quantity of which had become excessive. This alternation of a principle containing nearly half its weight of azote, with another containing no azote at all, is perhaps, one of the most singular facts occurring in physiology." p. 74.