B. ANALYSIS OF ANIMAL SOLIDS.
Solid matters, as turnours concrdtions, and sediments are best subjected to a preliminary test by the action of heat; the sedirnents are separated by filtration from the liquids in which they are deposited; by ignition on plati num foil of a few small fragments we observe either, 1. It is wholly or almost wholly dissipated, in which case it consists of, Cholesterin, which fuses and burns with flame ; Uric acid, or which are gradually dissi /Trate ammonia, $ paled, producing transient blaccyk es tniicngoxoifdethewfboiielhariosucnodn, sumed with a pe culiar odour; Albumen, fibrin, or hairs, which swell up and burn with flame: 2. Or it blackens, leaving a less bulky re sidue; In which case it may be Urate of soda, potash, they leave an alka Lime or magnesia, $ line ash, which in he two 'first fuses at a red heat, or it may arise rom a mixture of some of the preceding list ith some of those that follow.
3. Or, lastly, it undergoes little or no change n bulk, when it is composed of Phosphates of the earths; Carbonate of lime, or magnesia ; Oxalate of lime, which generally decrepi tes.
Having by these simple trials acquired some nowledge of the nature of the substance we ave to deal with, we proceed to a more spe 'al examination.
a. Choksterin is the principal constituent of "liary calculi in the human subject, mixed ith variable proportions of colouring matter. hese calculi, when numerous, generally pre facettes more or less flattened and po ,ffied ; when solitary, they often attain consi Lrable bulk, and are usually crystalline and mitransparent on the surface. Before the owpipe they fuse and bum with a bright oky flame, leaving hut little ash. Boiling hot dissolves the cholesterin, and on cool deposits the greater part in pearly glisten ing scales. Caustic potash dissolves the co louring matter and leaves the cholesterin. This last reaction distinguishes it from other fats, and particularly from lithofellic acid, recently discovered as an occasional constituent of be zoars and of gall-stones in the inferior animals; the lithofellic acid fuses at a higher tempera ture than cholesterin, and separates from its alkaline solution as an hisoluble fat on neu tralizing by a stronger acid.
b. Uric acid generally assumes the form of a reddish-brown crystalline sand, or of lighter coloured rounded masses. Before the bloW pipe it blackens and burns away, leaving only a minute trace of ash, usually alkaline, owing to the presence of a very srnall quantity of lime or soda. The manner of applying nitric acid, so as to produce the characteristic colour from the decomposition of uric acid, has been al ready mentioned. When powdered it dissolves completely in solution of potash by the aid of heat, and if the solution be supersaturated with hydrochloric acid, uric acid again preci pitates in minute white crystals.
The urates are much more soluble in hot water than uncombined uric acid : they form amorphous deposits usually of a light brown colour.
Urate of ammonia before the blowpipe pre sents phenomena resembling uric acid; when rubbed with solution of caustic potash, ammo niacal fumes are emitted. In its other reac tions, except that it is more soluble in boiling water, it closely resembles uric acid.
Urate of soda is distinguished by the large proportion of fusible alkaline ash left on igni tion after the application of a red heat; the residue dissolves with effervescence in hydro chloric acid and gives no precipitate when this solution is treated with an alcoholic solution of chloride of platinum. If potash were present, it would be indicated by the formation of crys tals on adding this test.
Urate of lime occasionally accompanies uric acid; the residue by incineration then yields the usual reaction's of lime, such as a precipitate with oxalate of ammonia when added to a solution of the ash in acetic acid.
c. Cystic oxide is wholly dissipated by heat, emitting a peculiar odour. • It is soluble readily both in acids and alkalies, and is deposited in hexagonal plates by spontaneous evaporation of its ammoniacal solution. The peculiar form of its crystal is at once recognized by the em ployment of the microscope.