4. Tubular casts are found in cases of albuminuria : of late some stress has been laid upon whether they present a smooth, homogeneous, transparent appearance, or whether they are stuffed with granular matter, as indicating two distinct conditions of kidney-disease; equal importance has been attached to their being in certain cases associated with oil globules. Independent of the uncertainty attending these observations (e. g., globular lithates having been unquestionably mistaken for fat), it does not appear that the student can derive any useful information from their dis crimination; and their relations seem at present to be subjects of study rather for men who are investigating the pathology of the kidney, than for those who wish to turn such knowledge to a practical account.
5. Vibriones may often be seen in active movement ; their pre sence is not connected with any particular forms of disease, but merely with chemical change in the urine.
6. The presence of spermatozoa may sometimes throw light on an otherwise obscure case.
Among crystalline substances we observe 1. Oxalate of lime.—This may be regarded as one of the most important ; not to much from the intrinsic value of the observa tion, as from the circumstance that we have no other means of detecting its presence with certainty. It occurs generally in octohedral crystals; occasionally we meet with some very short square prisms of uric acid, which closely resemble the oxalate of lime ; but with care this need never be any source of fallacy The planes of refracted light crossing the square surface diago nally, and disappearing and reappearing as the focus is altered, are extremely characteristic, and never seen under other circum stances.
2. Uric acid.—In combination with alkali the urates are chiefly seen under the microscope as amorphous granular matter, or assuming a variety of irregular rounded shapes. The observa tion that along with this deposit there are some defined crystals of uric acid, is of considerable value in treatment ; and this the microscope can alone determine vrith certainty ; the lozenge-shaped crystals and square prisms of the acid being quite distinctive. The same obserration will immediately solve any doubt as to the true uature of the sabulous deposit, which, in its nncombined form, lithic acid usually presents.
3. Triple phosphate.—The chemical test is of itself quite suf ficient to distinguish the presence of earthy salts; and the most common of these, the phosphate of lime, is rarely found in a crystallized form; like the urates, the phosphates are usually seen only as granular matter. The three-sided prisms with beveled ends, which characterize the triple phosphate, are not liable to be confounded with any other crystals. They indicate the presence
of an excess of free ammonia, and therefore the probability of partial decomposition of the urine ; but this rule must not be regarded as absolute, for cases occasionally occur in which it is caused by the secretion of alkaline urine.
These are the most important of the objects which microscopic examina tion revals. The list might be considerably added to, and the student. in learning the microscope, may often usefully employ his time in nnriddling some of the more complex or more rare phenomena, detailed in the various treatises on this subject, because by such means he acquires fainiliarity with the use of the instrument ; those just described are necessary for the purposes of diagnosis. If the chemical tests be rightly applied, pretty nearly all the facts regarding the simpler forms of sediments may be ascertained without the use of the microscope. It is in the complex cases, where 'there is any admixture, that its value becomes so great in discriminating the different objects, and showing the true character of each, when several distinct seta of chemical experiments might have been needed to accomplish the same end. It is particularly useful when the urine is generally optque, and the effects of chemical reagents on the sediment are less distinct. The presence or absence of blood-globules in the sediment, when the urine is dark colored, a large amount of epithelium, or some pus-globules, when it is milky, and the absence of any abnormal deposit when heat, acid, and alkali have alike failed to remove the haze after partial decomposition has begun, are each of rat value in confirmation of the chemical analysis. But, on the other hand, heat and acid will distinguish in a moment between the lithates and the phosphates in their amorphous condition—a conclusion which at best can only be guessed at by the employment of the microscope.
The microscope does not afford much assistance in determining the source of hemorrhage when blood is present. Tabular casts, mixed with blood-glo bules, would show that passive contrestion of the kidney accompanied the hiematuria; and this would be coincident with an excess of albumen ui the urine. Crystals of uric acid may lead to the suspicion of the existence of a calculus as its cause ; but it must be remembered that they are constantly found in the hiematuria of scarlatina' dropsy. In fungoid disease of the bladder, the compound cells of cancerous growth, and in chronic ulceration, pus-cells accompany the blood-globules when the hemorrhage is from the bladder. The changes in form which they undergo are dependent equally upon the chemical relations of the urine, and the period during which they have remained in it.