FECES. 547 



Consequently, the quantity of fixed matter given out of the sys- 

 tem in ten days exceeded the quantity taken in by 615-425 

 grains, 



The silica taken in amounted to, . 219*548 grains. 



That given out was only, . 185-266 



Remain, 34-282 

 Consequently, there disappeared 34-282 grains of silica. 



The phosphate of lime taken in was . 136-509 grains. 

 That given out was . . 274-305 



137-796 



Consequently, there must have been formed, by digestion, in 

 this fowl, no less than 137-796 grains of phosphate of lime, be- 

 sides 5 1 1 *9 1 1 grains of carbonate. Consequently, lime (and per- 

 haps also phosphorus) is not a simple substance, but a compound, 

 and formed of ingredients which exist in oat-seed, water, or air, 

 the only substances to which the fowl had access. Silica may 

 enter into its composition, as part of the silica had disappeared ; 

 but if so, it must be combined with a great quantity of some other 

 substance.* 



These consequences are too important to be admitted without 

 a very rigorous examination. The experiment must be repeat- 

 ed frequently, and we must be absolutely certain that the hen 

 has no access to any calcareous earth, and that she has not di- 

 minished in weight ; because, in that case, some of the calcare- 

 ous earth, of which part of her body is composed, may have been 

 employed. This rigour is the more necessary, as it seems pretty 

 evident, from experiments made long ago, that some birds, at 

 least, cannot produce eggs unless they have access to calcareous 

 earth. Dr Fordyce found, that, if the canary bird was not sup- 

 plied with lime at the time of her laying, she frequently died, 

 from her eggs not coming forward properly.f He divided a 

 number of these birds at the time of their laying eggs into two 

 parties : to the one he gave a piece of old mortar, which the little 

 animals swallowed greedily ; they laid their eggs as usual, and 

 all of them lived ; whereas many of the other party, which were 

 supplied with no lime, died4 



* Ann. de Chim. xxix. 61. f On Digestion, p. 25. 



\ Ibid. p. 26. 



