618 DIGESTION. 



to be unchanged; for fat cells were sometimes unaltered in the faeces ; 

 and crystals of cholesterin might generally be obtained from them 

 especially after the use of pork fat as diet. 



Of vegetable aliments, large quantities of cell membrane were unal- 

 tered; and starch cells were commonly deprived of only part of their 

 contents : the green colouring matter chlorophyll was unaffected, and 

 the walls of sap vessels and spiral vessels were usually found in large 

 quantities in the faeces, their contents having been probably removed 

 during digestion. 



The faeces differ in each animal species. Those of the herbivora con- 

 tain less animal matter than those of the carnivora and omnivora; and 

 the agriculturist is well aware, that the excrements of all animals are not 

 equally valuable as manure. The dung of the pigeon is alkaline and 

 caustic; and hence has been employed in tanning for softening skins. 

 The excrement of dogs, that have fed only on bones, is white, and ap- 

 pears to be almost wholly composed of the earthy matter of bone. It 

 has not, however, been examined by modern chemists. This white ex- 

 crement is the album graecum, cynocoprus, spodium Grrsecorum, album 

 canis or stercus caninum album, of the older writers. It was formerly 

 employed as a discutient to the inside of the throat in quinsies, but is 

 now justly discarded. 



M. Vauquelin, 1 on comparing the nature and quantity of the earthy 

 parts of the excrements of fowls with those of the food on which they 

 subsisted, arrived at some results that are of interest to the physiolo- 

 gist. He found that a hen devoured, in ten days, 11111*8-43 grains 

 troy of oats. These contained of phosphate of lime 136*509 grains ; 

 and of silica 219*548 grains; in the whole 356*057 grains. During 

 these ten days she laid four eggs, the shells of which contained 98*779 

 grains of phosphate, and 58*494 grains of carbonate of lime; and she 

 passed 185*266 grains of silica. The fixed parts, thrown out of the 

 system during the time, consisted of: 



Phosphate of lime, 274-305 grains. 



Carbonate of lime, 511-911 



Silica, 185-266 



Given out, 971-482 



Taken in, 356-057 



Surplus, . . . 615-425 



The quantity of fixed matter, therefore, given out of the system in 

 ten days, exceeded the quantity taken in by this last amount. 



The phosphate of lime, taken in, amounted to ... 136*509 grains. 

 That given out, to 274-305 



137-796 



There must, consequently, have been formed 137*796 grains of phos- 

 phate of lime, besides 511*911 grains of the carbonate. The inferences, 

 deduced from these experiments, were, that lime, and perhaps also phos- 

 phorus, is not a simple substance, but a compound formed of ingredients 



1 Annales de Chimie, torn. xxix. p. 3. 



