APPENDIX. 525 



abundant in uroxanthin, has become alkaline in the bladder. 

 Heller has noticed it in these sediments forming groups of 

 delicate prisms. (See Plate iii, figs. 37 and 38 a.) It like- 

 wise assumes this form when urine, abounding in uroxanthin, 

 is treated with nitric, sulphuric, or hydrochloric acid. In this 

 case it is principally found on the surface of the fluid. 



AVhen allowed to crystallize from its cold spirituous solution, 

 it forms groups which appear nearly black, but are blue and 

 transparent at the edges. (See Plate iii, fig. 38 , b.) 



Urrhodin appears to be a less oxydised product of uroxanthin 

 than uroglaucin, and usually occurs in much larger quantity. 

 It is most commonly observed in cases in which the urine is 

 alkaline before emission, in consequence of containing much 

 vcsical mucus, and its development in such cases is hastened 

 by the addition of nitric acid. The method of isolating it has 

 been already described. Heller has never succeeded in ob- 

 taining it from its spirituous solution in a crystalline form. It 

 occurs in granules, which, under the microscope, appear of a 

 beautiful rose-colour. It is resinous in its nature, and burns 

 with a clear flame. 



Heller concludes his paper (of which the above is but a brief 

 abstract) with a notice of some experiments on uroerythrin, the 

 ordinary pigment of inflammatory urine. 



On treating uric-acid crystals obtained from healthy urine 

 with cold alcohol, the pigment formed a carmine solution, and 

 the uric acid remained comparatively devoid of colour, being 

 of a yellowish-brown tint from the brown pigment of the urine. 

 The spirituous carmine solution on exposure to the air gra- 

 dually became purple, and had all the properties of uroglaucin, 

 previous to which it appeared to be identical with urrhodin. 



On treating the red sediment common in inflammatory af- 

 fections and tinged with uroerythrin, with hot and cold 

 alcohol and ether, the red pigment remained unaffected, unless 

 a little acid was added. The difference of solubility in the 

 above menstrua is therefore sufficient to separate uroerythrin 

 from urrhodin. 



Heller's theory of the production of uroglaucin and urrhodin 

 affords a satisfactory explanation of the occurrence of the blue 

 sediments noticed in pp. 274, 327, and 329. 



PAGE 137. Quantitative determination of urea. Two papers 



