Sometimes cystitis comes bn as a catarrh of the bladder, propa gated from the urethra, in cases of gonorrhoea; simple idiopathic catarrh is necessarily very rare.
The principal source of information is the condition of the urine itself; when pus is derived from the kidney, as a general rule the urine is acid, decidedly albuminous, and the pus falls as a sediment to the bottom ; when derived from the bladder, the urine is alkaline, the amount of albumen not so great, and the pus more or less altered in character, becoming ropy and resem bling mucus. Casual circumstances and the effect of treatment may alter these facts for a time, but, when observed in the first instance, or remarked as a usual condition, the evidence they afford, combined with the history of the case, are quite character istic of the true nature of the disease in each of its forms.
§ 7. Diabetes.—The chemical test for the presence of sugar is a very certain one if applied with sufficient care; but the whole cir cumstances connected with confirmed diabetes are so distinct that the diagnosis scarcely requirea this corroboration. Unfortunately there are few symptoms which can lead to its early detection, the amount of urine passed in the twenty-four hours is so little regarded by most persons that they seldom think of adverting to it till it be in very great excess; it is generally the existence of weakness and emaciation which excites the patient's attention ; sometimes the circumstance is observed that where the urine falls it leaves a white crust when it dries ; sometimes the unusual appetite and craving for chinks lead him to suspect that something is wrong.
To the eye of the practitioner the emaciation of diabetes is very different from that of other diseases ; it is not marked by any unhealthy appearances such as characterize the various cachectic states ; its combination with hunger may suggest the existence of intestinal worms, but in following the scheme for the examination of the patient laid down in the early part of this work, the very next inquiries lead us at once to the true ex planation. Along with the emaciation and craving appetite thirst is excessive, the urine is secreted in large quantity, the bowels are costive, and the feces dry and solid ; under no other condition of disease 'is the same train of symptoms ever remarked.
§ 8. Disordered Function.—Under the name of functional dis turbances must be included variations in the proportion of water and other normal constituents which, as they are elaborated else where, may pass out of the body through the kidneys without implying specifie disease of any portion of the urinary apparatus.
They e,annot be easily classed according to the diseases with which they are commonly associated ; but assuming that the history of the case and the examination of other organs has already led to an opinion being formed on its nature, we have to inquire what additional light may be derived from an examina tion of the urine.
Excess of water, while it constitutes the whole disease in what is called diabetes insipidus, and modifies the characters of the urine in other states of disease, is constantly observed in health after certain ingesta which stimulate the kidneys, and after an hysteric.paroxysm : it is really a matter of no great importance.
Deficiency of water is most remarkable in fevers, and in cases in which the perspiration is excessive : it is also observed when diarrhoea exists, and sometimes as an effect of dyspepsia, the urine becoming acid, scanty, and loaded, irritating the bladder and urinary passages. The secretion is also sc,anty when the renal circulation is interfered with by abdominal distension or disease of the heart, though very frequently in cases of the latter class there is more than mere functional disturbance— congestion, if not actual disease begun. In dropsy depending. upon disease of the kidney, the secretion is always diminished while anasarca is on the increase, partly as its cause, but partly too as its effect.
When the proportion of water falls much below the healthy standard, those salts which are more soluble in warm than cold water, if present in their usual amount, ought to be precipitated, forming a sediment: but here another law comes into play, be cause their chemical constitution varies with the amount of what, for convenience, we may term free acid or free alkali. If free acid be present, the lithates exhibit that form in which they are less soluble in cold than warm urine, and they are precipitated when the urine is scanty; if free alkali be present, their condition is changed, and they are held in solution at all temperatures. The deposition of phosphatic or earthy salts is not so dependent on the proportion of water, for they are very easily dissolved by free acid, and are very insoluble when free alkali is present: their solubility is unaffected by heat.