1 A patient may be so circumstanced, that the preservation of the faeces, for inspection, is attended with inconvenience. It is, therefore, worthy of notice, that a table-spoonful of sweet oil poured over them, by investing the surface with a film, effectually prevents evaporation, and the consequent stench they might otherwise occasion. This precaution should always be adopted in the wards of hospitals.

342. The examination of the urine is also a matter of considerable importance. Its appearance will not only assist us in forming a judgment respecting the seat of the dyspeptic disease; but, if carefully watched from day to day, will point out the beneficial changes which our plan of diet and medicine may have produced. It will also instruct us in the species of food which best agrees with the patient; for slight errors of diet, although imperceptible in other respects, are generally announced by obvious changes in the urinary deposites.

343. Without entering with chemical minuteness into the history of the changes which the urine under-goes under different conditions of the body, there are certain phenomena with which every practitioner ought to be well acquainted: these I shall briefly enumerate, and endeavour to point out the indications which they severally afford. The quantity evacuated during a given interval is the first question which presents itself; a diminished flow of deep-coloured urine is invariably associated with febrile action; while an increased quantity of pale urine more generally indicates a peculiar state of nervous irritability, unattended with fever. When urine of this description (Diabetes Insipidus) flows most copiously during the night, I have generally found it to be symptomatic of some affection of the brain. In estimating, however, this symptom, the practitioner will see the importance of inquiring into the vicarious excretion of the skin. Much has been written upon the subject of albuminous urine, or that in which a coagulum is produced by the application of heat; Dr. Blackall has maintained that it is connected with too great an action in some part of the system, and he considers that its occurrence in dropsy should be received as an indication of the necessity of blood-letting. I have met with several cases of dyspepsia, in which such a state of urine occurred, and I am disposed to believe with Dr. Prout that it is derived from the chyle.

I have, at this time, two patients under my care, who have long suffered from the effects of tuberculated lungs; and during the progress of the present work, I examined their urine, and found, in both cases, that it was albuminous. We have, probably, too few data to lead us to a safe conclusion with regard to the cause of the phenomenon; but I am, at present, impressed with a belief that it arises from imperfect sanguification; the chyle, not undergoing the necessary changes to convert it into perfect blood, is eliminated by the kidneys. It is essential, in every case of protracted dyspepsia, to inquire into the state of the urinary secretion, in order to ascertain whether the patient may not be labouring under diabetes; for this disease is far more common than is generally supposed. So many valuable works have appeared upon this subject, that I consider it unnecessary to enter upon its history; but I should not discharge my duty to the professional reader, were I to omit noticing the concise but luminous chapter with which Dr. Prout has favoured us, in his valuable work on the diseases of the urine.

344. But of all the changes of which the urine is susceptible, none perhaps are less equivocal, or more indicative of a deranged state of the alimentary functions, than the deposite of lithic acid, either in an amorphous or crystalline form. Dr. Prout states that this acid, when in the former condition, is always in some state of combination, generally with ammonia; but when in the latter, it is nearly pure. He observes, that in healthy urine the lithic salt exists in such a proportion, as to be held in permanent solution at all ordinary temperatures; but that, from particular causes affecting the health, its quantity is preternaturally increased, and the excess is deposited as the urine cools. Dr. Philip is inclined to account for its appearance in the urine from an increased quantity of acid passing-through the urinary organs: from this view of the subject the lithic acid deposited must be considered as arising, not from the excess of that substance in the urine, but from a decomposition of the compounds into which it enters, by the agency of a free acid.

He considers that, in a healthy state of the system, the precipitating acid is thrown off by the skin, and he supposes that, even when generated in excess, it may be diverted to the surface of the body by merely increasing the insensible perspiration; an opinion which is certainly strengthened by the admitted fact, that calculous affections are more frequent in cold and moist climates than in those regions where the cutaneous is in a state of predominant activity in relation to the urinary system.

But, from whatever cause the precipitation may take place, its occurrence must be considered as a very delicate test of alimentary disturbance. By watching the occurrence and disappearance of these deposites, we are enabled to form a very just conclusion as to the efficacy of any plan of medicine or diet that may have been prescribed. I am acquainted with a gentleman who can never eat bread without discovering a change in his urine. He told me that he had entirely overcome the lithic diathesis by substituting biscuits. To those who are not acquainted with the influence which the slightest error in diet possesses over the urine, this may appear a refinement scarcely within the bounds of credibility: Dr. Prout, however, has stated a parallel case. The variety of colour exhibited by the lithic sediments is also deserving of some attention, and the profession is under deep obligations to Dr. Prout for the able manner in which he has described such modifications. He arranges them under three divisions, viz. 1. Yellowish or nut-brown sediment; 2. Reddish-brown or lateritioits sediments; and 3. Pink sediment.