PLATE 12. — Crystals from Animal Secretions. 



Figure 



1. Uric acid, human, natural, a, rhombs, front view ; b, side view ; c, d, striated ; 



e, rhombs with obtuse angles truncated ; /, twin crystals ; g, ditto ; h, hour- 

 glass crystals ; i, nucleated ditto : /.-, /, m, n, o, aigrettes : p, large dumb- 

 bell forms. 



2. Uric acid, human, natural. a, front, b, side view. 



3. Uric acid, coloured artificially by murexide. 



4. Uric acid, natural, a, front, b, side view ; c, aigrette. 



5. Uric acid, precipitated from solution in sulphuric acid by water. 



6. Uric acid, rhombs, slightly acted upon with potash, showing spurious nuclei. 



7. Uric acid, precipitated from gout-stones. 



8. Uric acid of Boa, artificially precipitated, a — d, from solution in sixlphuric 



acid by water : e — h, from solution in potash by muriatic acid. 



9. Uric acid, precipitated from the excrement of the tortoise. 



10. Uric acid, precipitated : — a, from the excrement of the clothes-moth ; h, from 



stag-beetle (Lucanus cervus). 



11. Urate of soda and ammonia, a, spheres with nuclei and concentric rings, arti- 



ficial ; b, surface covered with radiating needles ; c, d, e, natural forms ; 

 /, r/, artificial. 



12. Urates of soda and ammonia, a, artificial urate of ammonia, deposited on 



cooling of an aqueous solution ; b, natural urate of soda, as composing the 

 chalky matter around gouty joiuts. 



13. a, b, Urate of lime. 



14. a, b, Urate of magnesia. 



15. Uric acid, precipitated by an acid from human urine. 



