COMPOSITION OF BURNED BONES. 417 



These proportions are not to be considered as constant, because it 

 varies not only in the different bones of the same animal but also in 

 bones from the same part of the body of different animals of the same 

 species. (Thomson^s Animal Chernistry, -p. 242.) But the existence of 

 such differences must render unhke the fertilizing action of the 

 bones of different animals — if, as many think, this action depends in 

 any great degree upon the quantity of phosphate of lime which they 

 respectively contain, 



4°. Besides the phosphate and carbonate of lime, I have stated that 

 bones contain certain other inorganic substances, which are found in 

 small quantity in the ash. What these substances are will appear 

 in the following table, which represents the constitution of the bones 

 of some animals, as analysed by Dr. Thompson : 



Ileum Ileum Vertebra, 



of a sheep. of an ox. of a haddock. 



Organic or combustible matter 43-3. 48-5 39-5 



Phosphate of hme 50-6 45-2 56-1 



Carbonate of lime . . .• 4-5 6-1 3-6 



Magnesia 0-9 0-2 0-8 



Soda 0-3 0-2 0-8 



Potash 0-2 0-1 — 



99-8 100-3 100-8 

 The soda exists in bones probably in the state of common salt, and 

 the magnesia in that of phosphate. An appreciable quantity of fluor- 

 ide of calcium, with traces of iron and magnesia, are also generally 

 found in bones, in addition to the substances indicated in the pre- 

 ceding analyses. 



5°. When bones are heated to redness in the open air the organic 

 part burns away, and leaves the white earthy matter in the form, and 

 nearly of the bulk, of the original bone. But if a dry bone be cover- 

 ed with dilute muriatic acid, the earthy or inorganic part is slowly dis- 

 solved out, and the organic part — the cartilage or gelatine — will alone 

 remain, retaining also the form and size of the organic bone. In this 

 state it is flexible and somewhat soft, and by prolonged boiling may 

 be dissolved in water, and manufactured into glue. 



This organic or combustible part of bones is identical in chemi- 

 cal composition with skin and glue, and is nearly the same as wool, 

 hair, and horn, of which the analysis has already been given. In 

 so far, therefore, as their efficacy depends upon the organic consti- 

 tuent, dry bones must be greatly inferior to an equal weight of any 

 of the other animal substances above described, because of the much 

 greater proportion of earthy matter they contain. 



§ 4. On what does the fertilizing action of bones depend ? 



Bones contain, as we have seen, a large proportion both of organic 

 and of inorganic matter ; — on which of these two constituents does 

 their fertilizing action most depend ? Some regard the phosphate of 

 lime or bone earth, as the only source of the benefits so extensively 

 derived from them — and it is by supposing the soil to be already suf- 

 ficiently impregnated with th s phosphate., that Sprengel accounts for 



