ELEMENTARY PHYSIOLOGICAL CHEMISTRY 



267 



Microscopically, however, it shows a distinct crystalline structure 

 consisting of hexagonal colourless plates or slabs (Fig. 158). 



2. Leucin and Tyrosin. Though very rarely, these two bodies 

 sometimes occur in urine (e.g. in severe hepatic disease), where their 

 appearance is similar to f-hat in a pancreatic digest (see Fig. 148). 



Fio. 161. Stellar phosphate of calcium, x 500. 



3. Hippuric Acid. This may appear in urine during the administra- 

 tion of benzoic acid. It crystallises in four-sided prisms. It is quite 

 common in the urine of herbivora. 



In Alkaline Urine the following may occur : 



1. Phosphates. Of these there are two kinds, viz., phosphate of 

 calcium and ammonium-magnesium phosphate. 



(a) Phosphate of calcium. The sediment is" chalky and never 

 pigmented; it clears up on adding a few drops of nitric acid; it is 

 increased by boiling. Microscopically it is usually amorphous, but 

 may exist as long prismatic crystals arranged in star-shaped clusters, 



