Chemical Changes in the Fermentation of Dung. 345 
It is impossible to reflect upon the liberation of these things 
from their prior combinations in the straw without admitting 
tlieir power to exercise an important influence in the process of 
fermentation, and when to these we add the alkaline bases con- 
tained in the excrements tliemselvcs we are prepared to regard 
them as important contributors to the general result. 
It is equally impossible not to be struck with the conservative 
influence of this mineral portion of our dungheaps. Potash, 
soda, and lime are calculated to unite strongly with and to retain 
the valuable phospiioric and sulphuric acids ; magnesia has the 
same power, and it can also combine with phosphates to form 
double salts. 
The well known affinity of oxide of iron, silica, and hydro- 
chloric acid for ammonia points out very clearl}^ the important 
service these substances may render as fixers of that valuable but 
volatile alkali. 
APPENDIX. 
Chemical Composition of the Solid and Fluid Excrements of Animals according 
to Sjjrengel. — (Stej^hens's ' Book of the Farm,' vol. i. p. 484.) 
Vegetable or woody fibre. 
Wax and resin. 
Cliloropbj'lle, or the green substance of leaves partly decomposed. 
Deposited humus. 
A fatty and oily substance. 
Mucus. 
A peculiar brown colouring matter, in the solid excrement of oxen. 
Vegetable albumen (hardened). 
Animal gelatine. 
Animal fibre. 
Salivary matter. 
Ozmazome. 
Hippuric acid. 
Uric acid. 
Lactic acid. 
Benzoic acid. 
Urea. 
Bilious matter. 
Bilious resin. 
Picromel. 
Oxides of iron and manganese, derived from vegetables. 
Earths, silica, lime, alumina, magnesia. 
Salts consisting of mineral acids and bases derived from plants and 
water. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
]8. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
Originating in the urinary passages. 
Common salt. 
Carburetted hydrogen. 
Phosphuretted hydrogen. 
Sulphuretted hydrogen. 
Ammonia. 
Hydro'fen. 
Products of the feimentation and putre- 
faction of the food in the bodies of 
animals. 
