been four open angles. This is a satisfactory explanation of the so-called tuberose (knollig, in German) appearance of artificial precipitates of the oxalate of lime.

Even regular crystals may become tuberose by apposition of new matter. So in the first deposit I found a crystal to the four pyramidal sides of which round masses were apposited. When these masses get larger, they form a sort of cap on each side of the prism, which when still larger makes them much like dumb-bells, with which indeed they are identical. Crossed dumb-bells (see centre of fig. 6, Pl. V) are large tuberose crystals.

Artificial oxalate of lime from urine.

Experiment 4.-To urine, which had just been emitted from the bladder, a solution of oxalate of ammonia was added. In the precipitate a great variety of crystalline forms were observed.

a. Small prismatic crystals, gradually rounding off intob. The ellipsoid and dumb-bell forms, the latter less prominent.

c. Squarish, flat bodies, with several indentures on two opposite sides. They appear as if formed by a number of ellipsoid bodies joined together with their flat sides.

d. Almost regular octahedra, the lateral edges not quite straight.

e. Crossed prisms or crossed octahedra. The types of all these crystals are represented in fig. 5 of Pl. V.

On standing in water for some weeks the crystals seemed to decay, particularly on their thin edges, which became much corroded. The development of vegetable growths made the formerly white precipitate green and dirty looking.

Experiment 5.-In this experiment not a single welldefined octahedron was obtained. The deposit consisted of granules of different shapes and sizes, the largest not exceeding 3% of an inch in their longest diameter. There was a tendency to straight, square outlines, in some cross markings were present. The deposit polarized as usual, white light being produced by the bodies. This urine was very acid, and the addition of the acid salt caused uric acid to crystallize in well-defined, large, four-sided rhombic plates, with right angles, polarizing in dark colours. This is the only instance in which I observed almost regular rhombic plates of uric

acid to crystallize out of urine, of a size and beauty equal to that of the finest artificially prepared uric acid.

Experiment 6.-The entire deposit consisted of octahedral crystals, with their angles and corners cut off, so as to make their outline to appear eight-sided; fig. 4, Pl. V, below coloured prisms. Most of the crystals were square; viz., their horizontal sides were equal, in some all eight sides were equal, in others the four secondary sides were shorter. In few specimens only two corners were cut off. Whether the new plane was one plane, or two forming an obtuse angle, I could not ascertain. In some apparently square crystals there was an octagonal marking, corresponding by four parallel sides to the original four sides of the octahedral form. In some it appeared as if the crystal had been divided by a plane falling through the four lateral edges, and one half had been turned upon the other half in an angle of 45° round an axis perpendicular upon the plane just described, representing a tropia, or turn, of the value of one eighth of the circle. The long axis (c) was = = 2, taking the short one (b) as 1. The crystals were very dark, and the cross was faintly illuminated.

Experiment 7.-The crystals obtained were long, crossed octahedra. The centre of the twins was occupied by octahedra of the ordinary appearance, and by crossed octahedra described in the former experiment. Assuming each octahedron to be a twin by crossing, there were here four or six crystals arranged round one common principal axis, each set being turned round the common axis in an angle of 30°, so that none of the horizontal axes of any one twin crystal coincided with the horizontal axes of the next one, but was distant from the secondary and ternary axes in the angle described. Four crystals crossing frequently formed eightrayed stars. Of the four secondary rays, sometimes only one, two, or three were present, giving the crystal an unsymmetrical appearance. Mixed with these regular crystals was a large proportion of roundish bodies polarizing in colours, attempts at ellipsoids, dumb-bells, and so on, many of which were twin crystals.

Experiment 8. After the addition of oxalate of ammonia to urine some caustic ammonia was added, until the fluid was alkaline. After standing over-night, a sediment had formed, and a thin crust was swimming on the fluid, consisting of radiated, zeolitic balls, baked together, which were of a yellowish colour and not affected by acetic acid.

They seem, therefore, to have been uric acid. The sediment was of a filmy nature, and consisted of numerous irregular prisms of ammonio-phosphate of magnesia, often crossed by two or three, and taking all the fitful appearances of this salt. Mixed with these were octahedra of oxalate of lime and other irregular polarizing undefinable bodies.

Experiment 9.-In this deposit many regular and irregular octahedral crystals were present, many simple twins, double twins; the corners sometimes very little prominent, or rounded off there were small crossed prisms. But the most regular crystals were large simple prisms, with apparently pyramidal terminations. The prisms, when seen edgeways, were flat, about one fourth or one fifth of their width in thickness. The dark ends on the prisms, when seen edgeways, corresponded to the planes terminating the plate; but on the large planes no octahedral planes were to be distinguished, so that the prisms could not be explained otherwise than as being prismatic plates, terminated by a horizontal prism.

Oxalate of lime occurring in urine spontaneously.

Observation 10.-Urine of a slightly dyspeptic man.-I put a sample of urine, which came acid and a little cloudy out of the bladder, to stand over-night. After sixteen hours a dense mucous cloud had settled at the bottom of the vessel, and, besides, a dense pink deposit of urate of soda had settled all over the cloud, and on the sides of the vessel. The mucus showed minute granules disposed all over its surface, distinct from the urate. There were many oxalate of lime crystals, but all only fragments of octahedra, mostly halves, and, when lying on their sides, showed the edge cut off by a prismatic plane, which latter reflected light when well focussed. These halves were most common. Then there were crystals with one edge regular, one corner cut off parallel to an octahedral edge, or parallel to an octahedral diagonal. There were irregular conglomerations of crystals of all shapes and sizes, from a roundish body to a regular hedgehog-like mass.

The irregular parts of the crystals seemed to have been those with which they were attached to their basis, which, most likely, was the mucus.

Case of so-called oxaluria.

Observation 11.-A gentleman, thirty-five years of age,

during the spring of 1856, had suffered from boils on various parts of his body, with some eczema now and then upon his arms. He had taken the sulphates of iron and magnesia, which, though they seemed to be borne badly by his digestive organs, improved his skin and general health so far that the boils disappeared. About the latter end of June, 1856, he became dyspeptic, his tongue got covered with a fur, and excoriations broke out along its sides, which he ascribed to the influence of the iron. His bowels became irregular, his mind depressed, his general health impaired. He then remarked a cloud in his urine a few hours after passing it; and, on examination, the cloud consisted of mucus with numerous octahedra of the oxalate of lime.

When he presented himself to me, he suffered from all the subjective symptoms described as characteristic of oxaluria. On inquiry, I found that he had read the description of that disease in Dr. Bird's work on Urinary Deposits,' at Mr. Pillischer's Microscope Rooms, which he used to frequent as an amateur of the microscope.

On August 21st, I examined the urine from twenty-four hours. It was yellow, acid, and quite normal. The cloud at the bottom contained many octahedra imbedded in the mucus, in which a great number of thread-like vibriones were moving about, particularly at the borders of the mucous masses, where the medium was more dilute, and therefore seemed to allow of their more free movements. They seemed to have a connection with beginning decomposition of the

mucus.

Average length of sides of octahedra 63% of an inch. (See Pl. II, fig. 4, crystals on the upper left.)

Experiment 12.-A part of the urine from the foregoing case was filtered, and some oxalate of ammonia added to it. The deposit obtained after six hours' standing was made up of octagonal crystals. They were more or less regular, became irregular with rough edges and rough surfaces, and then baked together in irregular rough masses. Mixed with those octahedral and irregular crystals were numerous prisms, some with double outlines, some very thin, and others very short. These prisms were very much like those in the first experiment with chloride of calcium. The whole deposit polarized in even so weak a light as that of a composite candle reflected from the mirror of the microscope, and, as usual, the more regular a crystal was, the less did it polarize.

Oxalate of lime in decomposing urine.

Observation 13.—A sample of ordinary yellow, acid urine, from a man enjoying average health, was put in an open beaker, and allowed to stand in my laboratory during six days of cool August weather. After the lapse of that time the cloud, which had settled on the day after it was passed, and had not been microscopically examined, had increased in density; and the urine had become turbid, and covered with a skim, in which there were some vegetable growths perceptible.

The sediment, which was pulverulent, after being shaken, always settled quickly to the bottom of the beaker. It consisted of octahedra of the oxalate of lime, of very small dimensions indeed, so that their true outline was only distinctly visible when perfectly in focus. Mixed with the octahedral forms were irregular small prisms, and few crossed prisms. The crystals frequently appeared as if one side or edge had been eaten out, or had not been perfectly formed. Others were roundish, and corresponded to the lumpy masses of pure artificial oxalate. Some small ellipsoidal bodies were present. Very minute animalculæ, or monads, were in constant motion through the fluid, and appeared as gray, dark points.

On seeing the oxalate sitting firmly on the particles of mucus, as if it had been formed out of them, and seeing only the free sides (planes, angles, and edges) perfectly developed, the other portions turned towards the mucus however always irregular, I could not help thinking that the mucus might have a share in the production of the oxalate.

Crystals of Oxalate of Lime from Urinary Calculi.

Though the greater proportion of the oxalate of lime calculi have an amorphous or only crystalline texture, there are some not very rare specimens, which on their surface are covered with the most perfect crystals. Mr. Quekett kindly afforded me an opportunity of closely examining several such calculi contained in the museum of the Royal College of Surgeons.

C. 34. Presented by Mr. Luke. A reddish brown calculus, is covered with white glistening crystals. They are octahedra, the principal axis of which is not much shorter than the two horizontal ones. The principal axis of the crystals averages in length from about one fortieth of an inch to one eightieth of an inch.

C. 35. Presented by Mr. Luke.

In this specimen the