At the time of its discharge the urine of the horse differs in its appearance on different occasions. In colour it varies from a pale-yellow to a deep brownish-yellow. It is usually transparent, but frequently turbid, and occasionally distinctly muddy and opaque. It has a strong, disagreeable odour and a saltish taste. When allowed to rest, a dullish gray precipitate is thrown down, consisting chiefly of calcic carbonate (fig. 134). Its reaction is alkaline, and on the addition of an acid, free effervescence is induced.

The specific gravity varies between 1.015 and 1.050. Microscopically examined, the sediment thrown down in repose is found to be made up chiefly of spherical, oval, and dumb-bell crystals of calcic carbonate, occasionally also octahedra of calcic oxalate, with a few epithelial cells from various parts of the mucous tract of the urinary apparatus.

The following two analyses given by Von Bebra show the composition of the secretion: -

I

ii

Water...

885.09

912.84

Solid constituents ...

114.91

87.16

Urea.....

12.44

8.36

Hippuric acid...

12.60

1.23

Uric acid...

-

-

Mucus...

0.05

0.06

Alcohol extract...

25.50

18.26

Water extract...

21.32

19.25

Soluble salts...

23.40

4000

Insoluble salts...

18.80

The .sediment obtained after the fluid has been allowed to rest is shown by three analyses to consist of organic and inorganic matter in the following proportions: -

I

11

1ll

Carbonate of lime

80.9 ...

... 87.2 ..

.... 87.5

Carbonate of magnesia ...

12.1 ..

7.5 ..

.... 8.5

Organic matter ...

7 0

5.3 ..

4.3

100.0 ...

... 100.0 ...

... 100.3

It will be seen from the above that urine is a highly complex fluid, comprising organic and inorganic constituents in a state of watery solution.