FATS. 69 



e. Fermentation test. The development of tlie vinous fermen- 

 tation on the atldition of a little ferment or yeast to a fluid, has 

 long been applied as a test for the detection of sugar. It was suc- 

 cessfully employed by Professor Leopold Gmelin of Heidelberg ' 

 for the detection of sugar in the animal fluids after the inges- 

 tion of amylaceous food. Dr. Christison has the merit of 

 particularly suggesting the application of fermentation for the 

 discovery of a diabetic state of the urine. 



When a little yeast is added to healthy urine exposed to a 

 temperatm-e of about 80*^-, no other change occurs for some 

 time, except the development of a portion of carbonic acid me- 

 chanically entangled in the yeast. When sugar is present in 

 the urine thus treated, it soon becomes troubled, a tolerably 

 free disengagement of bubbles of carbonic acid takes place, and 

 a frothv scum forms on the surface of the fluid, which evolves 

 a vinous odoiu*. These changes take place with great rapidity, 

 even when the quantity of sugar present is very small. If the 

 evolved carbonic acid is collected, the quantity of sugar in the 

 urine may be determined by measuring it, as a cubic inch^ of 

 the gas very nearly corresponds to a grain of sugar. 



In the absence of a mercm'ial trough, the carbonic acid may 

 be determined by the increase of weight^ of Liebig's bulb-appa- 

 ratus, charged with a solution of potash. 



f. Test afforded by the growth of the torula. If urine 

 containing the smallest proportion of sugar be exposed for a few 

 hours to a temperature above 70", and a drop taken from the 

 surface be examined under the microscope, numerous very mi- 

 nute ovoid particles will be discovered. In the course of a few 

 horn's more they become enlarged, and appear as distinct oval 

 vesicles, which rapidly become developed into that species of 

 confervoid vegetation, to which the term torula has been applied. 



2. Fats. 

 Under the name of " fats," we include various non-nitro- 

 genous compounds, which are insoluble in water, but soluble 

 in hot alcohol and ether. 



' Recherches Experimentales sur la Digestion. Paris, 1826. Part I, p. 202. 



2 100 cubic inches of carbonic acid gas coiTCspond with 106-6 grains of diabetic 

 sugar. 



3 100 grains of carbonic acid indicate 225 grains of diabetic sugar. The gas must 

 be passed through a tube containing chloride of calcium. 



/ 



