344 DR. BENCE JONES ON THE VARIATIONS IN 



blue paper be used, this, whilst wet, will retain its colour ; but if the test-paper be 

 left to dry in either case it will be found that a change takes place. From the red- 

 dened litmus paper first used the blue colour will disappear, whilst the blue paper, 

 when quite dry, will become red in consequence of a slight decomposition of the am- 

 moniacal salt. This decomposition I have elsewhere shown to be the result of the 

 evaporation of all ammoniacal solutions, and thus a ready and easy way is afforded 

 of determining in any case of the alkalescence of the urine, whether it is caused by 

 some ammoniacal salt, or whether it results from the presence of some fixed alkali*. 



It not unfrequently happens that alkalescence is caused by fixed alkaline salts in 

 those who, though not ill, yet suflfer from indigestion whilst leading sedentary lives. 

 I have more especially observed it where the octahedral crystals, usually supposed to 

 be oxalate of lime, have been present. After a breakfast consisting chiefly of bread, 

 in an hour and a half the water passed may be found healthily acid to test-paper, but 

 that which is next passed, that is, from two to four hours after breakfast, will have 

 an alkaline reaction. Frequently blue test-paper will be found, when dry, to undergo 

 no change from the action of such urine. It will remain of nearly as deep a blue as 

 before when the fluid has perfectly evaporated. This urine when passed will, though 

 alkaline, often be perfectly clear, and if it be heated a granular precipitate will fall, 

 the fluid becoming turbid from the deposit of earthy phosphates, which dissolve in 

 dilute hydrochloric acid, usually without any effervescence. 



Such a precipitation by heat takes place when the urine is not even neutral. It 

 may be slightly acid. When boiled a precipitate falls, and if the fluid is then tested 

 it is found to be more acid than before. If such a deposit from acid urine is left to 

 become cold, the earthy phosphates are found to be partially, and sometimes even 

 entirely redissolved, being again precipitable by boiling, and again partially or en- 

 tirely dissolving on cooling. 



If such urine as I have mentioned is passed alkaline and thick from deposit, it 

 will be found, if immediately examined by the microscope, to be entirely granular 

 (Plate V. fig. 2), the supposed form of phosphate of lime. Dilute hydrochloric acid, if 

 added occasionally causes an effervescence, which in some cases arises from some 

 alkaline carbonate in solution. 



If the alkalescent or neutral urine is left for some hours, the surface becomes 

 covered with an iridescent pellicle (fig. 1). This examined with the microscope 

 contained here and there a long prismatic crystal, but the pellicle itself consisted of 

 plates covered with spots of amorphous deposit. Some of these were triangular, 

 some quadrilateral, some with regular and others with a ragged margin. The iri- 

 descence depended on these plates, which probably consist of phosphate of lime, as 

 in some cases not a single prismatic crystal has been visible. 



In some who suffer from indigestion the deposit of amorphous phosphate is con- 



* This method, however, I have found to fail when, much urate of ammonia and only a small quantity of 

 fixed alkali chanced to he present. 



