184 THE SECRETIONS: 



and the weight of urea calculated from it. By subtracting the 

 weight of urea from that of the whole of the alcohol-extract, we 

 obtain as a residue the lactates, chloride of ammonium, alcohol- 

 extract, and lactic acid, if any should be present. 



The uric acid must be determined from a separate portion of 

 urine. If any sediment occurs in the urine, it must be separated, 

 and its weight ascertained in relation to the weight of the urine. 

 After having ascertained its general nature, its various consti- 

 tuents must be determined by the methods already given. 



If the morbid urine contains substances which do not occur 

 in the healthy secretion, this method will even then often hold 

 good, since the abnormal ingredients are sought for by inde- 

 pendent processes. In many cases, however, a change is requisite; 

 and I shall proceed to notice the various cases that may occur. 



1. Qualitative and quantitative determination of substances 

 which do not occur in normal urine. 



Albumen is frequently present in the urine of persons suf- 

 fering from disease, and indeed I once found it in the urine of 

 a healthy vigorous young man, aged twenty-six years. If there 

 is a considerable amount of albumen, nitric acid or bichloride of 

 mercury will cause a precipitate, and the urine will become 

 turbid on the application of heat, and deposit flocculi of coagu- 

 lated albumen. Urine of this sort is usually pale and slightly 

 turbid from containing mucus in suspension : its colour may, 

 however, be high, as in the phlogoses ; it may have an acid, 

 neutral, or alkaline reaction, a high or a low specific gravity. 

 When the quantity of albumen is very small, the application of 

 heat is the most efficient test, and the most minute quantity of 

 albumen may be readily detected by observing the uppermost 

 part of the column of the fluid as it is being gently heated in 

 a test-tube. When the temperature is sufficiently elevated, the 

 coagulation begins to occur in the form of small white nebula?, 

 which are dispersed by the rising of large bubbles, and the general 

 turbidity of the whole fluid is often so slight that unless the de- 

 velopment of these nebulae has been observed at the commence- 

 ment of the process, it becomes a matter of difficulty to decide 

 upon the presence of albumen. It is only in cases in which 



