44 INORGANIC PROXIMATE PRINCIPLES. 



the softer tissues, it forms more than one-half the substance of the bones. 

 It is estimated by Barral, that the osseous tissues constitute 6.4 per 

 cent, of the entire mass of the body ; and the lime phosphate forms on 

 the average from 51 to 58 per cent, of the substance of the bones. This 

 would give, for a man weighing 65 kilogrammes, or 143 pounds avoir- 

 dupois, 2400 grammes of the calcareous salt in the whole body. Its 

 proportion in various tissues and fluids of the human system is as 

 follows: 



QUANTITY OF LIME PHOSPHATE IN 1000 PARTS IN THE 



Enamel of the teeth . 885 Milk .... 2.72 



Dentine . . . .643 Blood .... 0.30 



Bones . . . 576 Bile .... 0.92 



Cartilages ... 40 Urine . . . .0,75 



Notwithstanding, therefore, the large quantity of lime phosphate in 

 the body as a whole, it is evident, from an inspection of the preceding 

 list, that nearly all of it is deposited in the more solid tissues ; while it 

 is present in but slender proportion in the animal fluids. Of these 

 fluids it is the milk alone which contains lime phosphate in notable 

 quantity, and here it is plainly subservient to the ossification of the 

 growing bones of the young infant, for whom the milk is used as food. 

 In the circulating fluids, the internal secretions, and the urine, on the 

 other hand, the calcareous salt is in small amount. Its importance in 

 the body depends mainly upon its simple physical property of impart- 

 ing rigidity to the solid tissues, rather than upon its active qualities in 

 the general phenomena of nutrition. 



In the solid tissues it is associated with other earthy and alkaline 

 salts, but preponderates largely over them in amount. In the bones, 

 the quantity of lime phosphate is from 5 to 6 times greater than that of 

 all the other mineral ingredients taken together. 



In the bones, teeth, and cartilages, the lime phosphate exists in a 

 solid form ; not, however, deposited mechanically in the osseous or 

 cartilaginous substance as a granular powder, but intimately united 

 with the animal matter of the tissues, like coloring matter in colored 

 glass, the union of the two forming a homogeneous material. It is not, 

 on the other hand, so combined with the animal matter as to lose its 

 identity and constitute a new chemical substance, as where hydrogen 

 combines with oxygen to form water ; but rather as salt unites with 

 water in a saline solution, both substances retaining their original charac- 

 ter and composition, though so intimately associated that they cannot 

 be separated by mechanical means. The lime phosphate, therefore, may 

 be extracted from a bone by maceration in dilute muriatic acid, leaving 

 behind the animal substance, which still retains the original form of the 

 bone or cartilage. 



In all the solid tissues the lime phosphate is useful by giving to 

 them their proper consistence and solidity. For example, in the ena- 

 mel of the teeth, the hardest tissue of the body, it predominates very 



