Species of Calculi.

External characters.

Chemical composition.

Remarks.

1.

Lithic of Uric.

Form, a flattened oval. S. G. generally exceeds 1.500. Color, brownish or fawn-like. Surface, smooth. Texture, laminated.

It consists principally of lithic acid. When treated with nitric acid a beautiful pink substance results. This substance is slightly soluble in water, abundantly so in the pure alkalies.

It is the prevailing species; but the surface sometimes occurs finely tuberculated. It frequently constitutes the nuclei of the other species.

2.

Mulberry.

Color, dark brown. Texture, harder than that of the other species. S G. from 1.428 to 1.976. Surface, studded with tubercles

It is oxalate of lime, and is decomposed in the flame of a spirit lamp, swelling out into a white efforescence, which is quick lime.

This species includes some varieties, which are remarkably smooth and pale-colored, resembling hempseed.

3.

Bone earth.

Color, pale brown or gray. Surface, smooth and polished. Structure, regularly laminated; the laminae easily separating into concrete crusts.

Principally, phosphate of lime. It is soluble in muriatic acid.

4.

Triple.

Color, generally, brilliant white. Surface, uneven, studded with shining crystals, less compact than the preceding species. Between its laminae small cells occur, filled with sparkling particles.

It is an ammoniaco-magnesian phosphate, generally mixed with phosphate of lime. Pure alkalies decompose it, extracting its ammonia.

This species attains a larger size than any of the others.

5.

Fusible.

Color, grayish white.

A compouud of the two foregoing species.

It is very fusible, melting into a vitreous globule.

6.

Cystic.

Very like the triple calculus, but it is unstratified and more compact and homogeneous.

It consists of cystic oxide Under the blowpipe it yields a peculiarly fetid odor. It is soluble in acids and in alkalies, even if they are fully saturated with carbonic acid.

It is a rare species.

7.

Alternating.

Its section exhibits different concentric laminae.

Compounded of several species, alternating with each other.

8.

Compound.

In characteristic form.

The ingredients are separable only by chemical analysis.