URINE. 197 



which, according to Boucharday corresponds exactly in its be- 

 haviour towards yeast, and in its solubility in spirit, with sweet 

 sugar, and may be separated in the same manner. 



I have had one opportunity of examining diabetic urine, 

 containing a slightly sweet sugar which was soluble in spirit, 

 and also a considerable amount of insipid matter which was 

 precipitated by alcohol, and appeared to resemble gum mixed 

 with water-extract and mucus. I could not separate it from 

 the water-extract, which is usually very scanty in diabetic urine. 



9. Carbonate of ammonia. 



In some diseases, especially in affections of the brain and 

 nervous system, and of the bladder and kidneys, the urine pos- 

 sesses the property of becoming quickly alkaline; indeed I have 

 observed instances in which it was alkaline at the period of its- 

 being passed. In these cases it has a very disagreeable, am- 

 moniacal odour, and changes red litmus paper to a bright blue. 

 In colour it may be either light or very dark ; it ordinarily 

 forms, in the course of a short time, a sediment of a grayish- 

 white, and occasionally of a yellow or red colour, consisting 

 of earthy phosphates. A certain test for the presence of car- 

 bonate of ammonia is afforded by holding a glass rod moist- 

 ened in non-fuming hydrochloric acid over the urine ; its 

 existence is indicated by the formation of dense white vapours. 

 On the addition of nitric acid to the filtered urine, numerous 

 bubbles of carbonic acid gas are briskly developed. After a 

 little practice the odour will be a sufficient indication of a 

 very minute quantity of carbonate of ammonia. The quan- 

 titative analysis of this substance is seldom undertaken, but 

 without doubt it is of importance, especially for the purpose 

 of ascertaining whether an increase in the quantity of carbonate 

 of ammonia necessarily involves a decrease in the amount of urea. 



I have satisfied myself that in diseases of the spinal cord, 

 when the urine often contains much carbonate of ammonia, it 

 is formed at the expense of the urea. In four experiments, 

 instituted with this object, I found scarcely a trace of urea in 

 the urine. 



An approximation to the amount of carbonate of ammonia 



1 [Bouchardat now regards this tasteless sugar as a compound of the ordinary 

 diabetic sugar with salts.] 



