446 THE INORGANIC MATTER CONTAINED IN BONES. 



§ 3. Of the composition of hones. 

 Few substances have of late years done so much to increase the 

 agricultural produce of various parts of England as the use of crushed 

 bones for manuring the land. 



1°. Recent bones contain a variable quantity of water and fat. 

 The proportion of fat depends upon the position of the bone in the 

 body, and upon the condition of the animal. The proportion of water 

 depends partly upon the solidity of the bone and partly upon its age. 

 According to Denis, the radius of a female, 



Aged 3 years, contained 33-3 per cent, water, with a httle fat 



Aged 20 years, " 13-0 " " 



Aged 78 years, " 15-4 " " 



The quantity of water thus present in bones performs an important 

 part in determining the action which bone-dust is known to exercise 

 upon the land. The oil is sometimes extracted by boiling the bones. 

 During this boiling they absorb more water, and thus, when laid upon 

 the land, undergo a more rapid decomposition, and exercise, in conse- 

 quence, a more immediate and apparent, and therefore, as some may 

 think, a more powerful and fertilizing action. 



2°. But bones differ from the other animal substances already de- 

 Bcribed chiefly by containing a much larger proportion of inorganic 

 matter, or by leaving, when burned, a greater percentage of ash. 

 The quantity of inorganic matter, however, contained in bones is not 

 constant. It is less in the young than in the full-grown animal — less 

 m the spongy than in the compact or more solid bones — and less in 

 those of some animals than in those of others. Thus, when freed 

 from fat and perfectly dried — 



Of inorganic matter. 



The lower jaw-bone of an adult left 68-0 per cent. 



a child of 3 years. — 62-8 " 



A compact human bone — 58-7 " 



A spongy human bone ; — 50-2 " 



The tibia of a sheep — 48-03 « 



The vertebrse of a haddock — 60-51 " 



It is obvious that the relative efficacy of equal weights of bones 

 must be affected by such differences in the relative productions of 

 organic and inorganic matter which they severally contain. 



3°. This inorganic matter or ash consists in great part of phosphate 

 of lime (Lee. IX., § 4,) but it contains also a considerable though 

 variable proportion of carbonate of lime, with smaller quantities 

 of several other ingredients. The proportion of carbonate of lime 

 appears to be smallest in carnivorous animals. 



Thus, for every 100 parts of phosphate of lime there exists in — 



Human bones about 20-7 carbonate of ime. 



Bones of the sheep 24-1 " 



Do. ox 13-5 « 



Do. fowl 11-7 « 



Do. haddock 6-2 « 



Do. frog 5-8 «* 



Do. lion 2-6 " 



