HUMAN F^CES AS A MANURE. 271 



sulphate of magnesia the proportion of such salts may rise to 

 20 per cent, the great mass being phosphate of magnesia, asso- 

 ciated with a small quantity of phosphate of lime and a little 

 iron. From Marcet's experiments, a new organic substance, 

 possessing an alkaline reaction, appears to exist in the human 

 fa3ces, to which the name " excretine " has been given. It is 

 crystalline, insoluble in water, sparingly soluble in cold alcohol, 

 but freely soluble in ether. It contains nitrogen and sulphur 

 in small proportions. Marcet regards excretine as one of the 

 immediate principles of the faeces existing in them, for the 

 most part, in a free state. The excrement of a healthy man 

 was found by Berzelius to consist of 



Water, 733 



Albumen, ...... 9 



Bile, ... ... 9 



Mucilage, fat, and other animal matters, . . 167 



Saline matter, . . . . .12 



Undecomposed food, ..... 70 



1000 



Such excrement, when freed from water, left 132 of ash in 

 1000 parts ; the ash consisted of 



Carbonate of soda, ..... 8 



Sulphate of soda, with a little sulphate of potash and 



phosphate of soda, ..... 8 

 Phosphate of lime and of magnesia, and a trace of 



gypsum, . . . . . .100 



Silica, . . . . . . .16 



132 



Considered as a manure, man's excrement, or nightsoil, con- 

 tains about three-fourths of its weight of water ; when ex- 

 posed to the air it undergoes very rapid decomposition, and 

 gives off much volatile matter, consisting of ammonia, carbonic 

 acid gas, and of sulphuretted and phosphoretted hydrogen 



