THE EXCRETION OF PHOSPHORIC ACID.
Phosphoric acid to the amount of from two to three grams is ex creted in the urine in twenty-four hours. It is combined partly with sodium, potassium, and ammonium to form soluble phosphates, and partly with lime and magnesia to form salts, which, though soluble in the natural acid of the urine, are quickly thrown down when the secretion becomes neutral or alkaline. The former group never forms urinary deposits, but the latter constitutes the earthy phosphates which are the chief features of phosphaturia and of advanced urinary concretions. It is unnecessary to make a separate estimation of these two groups, in order to gauge accurately an excessive elimination of phosphate. It is sufficient to estimate the amount of phosphoric acid.
The Earthy Phosphates.—Phosphoric acid is spontaneously de posited in the urine in one of the three following combinations (Roberts) : 1. Amorphous phosphate of lime, or bone earth ; 2. Crystallized phosphate of lime (CaTIP0,-F2Aq) ; 3. The triple phosphate, ammonio-magnesium phosphate (Mg IsTII,P0, +6Aq) .
1. Amorphous Phosphate of Lime.—The occurrence of this deposit merely denotes that the urine has been rendered alkaline by a fixed alkali, as when the carbonates of potash and soda are present in ex cess. It forms an amorphous white flocculent deposit, which is increased by heat and dissolves rapidly in any acid. There is gen erally an iridescent film, "a gas tank" film on the surface. Micro scopically, the deposit consists of minute granules aggregated into clumps.
It is chiefly found in patients who have taken large closes of alkalies. It is the normal deposit of alkaline urine, and its clinical significance and treatment depend on the cause of the alkalinity of the urine.
2. Crystallized Phosphate of Lime, or Stellar Phosphates.—The occurrence of a deposit of stellar phosphates is rare. Hassall first called attention to this form of urinary deposit in 1860, and Sir Wil liam Roberts, who re-examined the question in 1862, reported as follows : The prevailing appearance is that of crystalline rods or needles, either lying loose or grouped in stars, rosettes, fans, or sheaf-like bundles (vide Fig. 68). Some of the crystals are club- or bottle-shaped and abundantly marked with lines of secondary crystallization.
The occurrence of a deposit of the stellar phosphate in urine is not common. It is, in fact, a rare deposit as compared with oxalate of lime, uric acid, or the triple phosphate.
The presence of this deposit in any quantity is, according to Sir W. Roberts, an accompaniment of some grave disorder. He has met with it in diabetes, cancer of the pylorus, once in phthisis, and more than once in patients exhausted by obstinate chronic rheumatism.
The crystals may, however, under peculiar conditions, be precipi tated in healthy urine. "When the urine is rich in lime, and its acidity is at the same time depressed to near the neutral line, stellee of phosphate of lime may form quite independently of any grave dis order, merely as the result of a coincidence in the chemical composi tion and reaction of the urine; for example, if after a full meal the acidity of the urine becomes greatly reduced, and lime derived from the food is present in excessive proportion. Under such circumstan ces, I have several times detected stellie of phosphate of lime, but only in small numbers. A depressed acidity of the urine is an es sential contingent to the formation of these crystals, and if the urine subsequently to their formation increase in acidity, they may spon taneously disappear." 3. The Phosphate of Ammonia and Magnesia, or the Triple Phos phate.—This insoluble crystalline compound is most usually encoun tered with the amorphous phosphate of lime. It is easily soluble in acids, and yet it may be found in urine which is feebly acid. If alone, the deposit has a fine crystalline, sugar-like appearance, and sparkling crystals may float in the urine and adhere to the sides of the vessel or form a glaze upon the surface. The usual form is the well-known coffin-lid-like crystal, a triangular prism with bevelled ends, but the edges and sides are often eroded by the action of an acid flow from the healthy kidneys, and the crystals assume a great variety of appearance in consequence. I have encountered this rare deposit alone and in fresh non-ammoniacal urine a few times only in surgical practice. The most startling instance was in a boy aged eight who consulted me on account of hrematuria of a painless and profuse character, which was proved to be due to fibro-sarcomatous polypi of the bladder. It is most often met with in urine which has become alkaline from volatile alkali. * This depends on the breaking up of the urea into carbonate of ammonia, by means of a ferment (micrococcus ure) generally introduced by the surgeon and increased by the alkaline conditions and the mucous discharge from the bladder which it excites. Carbonate of ammonia at once throws down the earthy salts, and the triple salt of ammonia-magnesium phosphate results. Sometimes when a large amount of pus is present it may be acted upon by the alkalies to produce thick ropy masses of muco pus. It affords at one and the same time an evidence of fermen tation, of ammoniacal urine, and of some severe catarrhal affection of the urinary tract.