INORGANIC SUBSTANCES. 103 



ble amount of the Carbonate; the proportion which the latter salt bears to the 

 former being greater in young animals than in old. 1 Thus, according to Leh- 

 mann, the ratio of the carbonate to the phosphate is as 1 : 3.8 in the Bones of 

 a new-born child, as 1 : 5.9 in those of an adult male, and as 1 : 8.1 in those of 

 an old male. So, according to Lassaigne, the proportion in the Teeth of a new- 

 born child is as 1 : 3.6, in those of a child six years old as 1 : 5.3, in those of 

 an adult as 1:6, and in those of an aged man as 1 : 6.6. In the enamel of 

 human teeth, according to Yon Bibra (pp. cit.), the proportion is as 1 : 20.5. 

 It is worthy of note that the massive skeletons of the inert Polypifera and Mol- 

 lusca are consolidated by carbonate of lime, almost to the complete exclusion of 

 the Phosphate ; whilst the comparatively light and thin calcareous casing of the 

 Crustacea, which, like the osseous skeleton of Vertebrata, serves for the attach- 

 ment of the muscles that move the body, and therefore needs considerable 

 strength in proportion to its substance, contains an appreciable amount of the 

 phosphate. In phleboliths and other abnormal calcareous concretions, creta- 

 ceous tubercles, &c., the proportion of carbonate of lime is usually high. It is 

 curious that carbonate of lime should normally present itself in a crystalline 

 form, in a certain part of the human organism, namely, within the membranous 

 lining of the vestibule of the ear, on the inner surface of which it is deposited, 

 the crystals being sometimes contained within cells. They are very minute, so 

 as even to exhibit the molecular movements characteristic of particles of very 

 small dimensions ; yet their crystalline form may be determined to be that of a 

 prism derivable from the rhombohedron of calc-spar. Crystals of this nature 

 occur much more frequently and abundantly among the lower animals, both in 

 the organs of hearing and in other parts ; thus among the Batrachia they are 

 found in the membrane of the brain, and in that which lines the intervertebral fora- 

 mina. For the sources of carbonate of lime in the animal organism, it is not 

 requisite to go far to seek ; since, almost all the water which is used as drink 

 contains an appreciable portion of it, and in the waters that have percolated 

 through calcareous soils, the amount of this salt is very considerable. More- 

 over, lime is taken in by all herbivorous animals, in combination with vegeta- 

 ble acids ; and these salts are converted into carbonates within the body ; so 

 that the carbonate of lime, if not converted into a sulphate, muriate, or phos- 

 phate, is excreted as such by the urine, in which it consequently appears occa- 

 sionally in large quantities. This substance is probably held in solution in the 

 animal fluids (as in ordinary spring water) by free carbonic acid ; but the chlo- 

 ride of sodium, and other alkaline salts which they contain, may exert an addi- 

 tional solvent power. Of this substance it may be remarked, in conclusion, that 

 there is no evidence of its subserviency to any other than a mechanical purpose 

 within the living body. 



78. With the foregoing calcareous salts, a small quantity of Phosphate of 

 Magnesia is almost invariably associated. It is chiefly found in the bones ; and 

 its proportion is somewhat larger in the bones of herbivora than in those of car- 

 nivora, the largest proportion presenting itself in the teeth of Pachydermata. 

 The ash of all the animal fluids and tissues contains a little phosphate of mag- 

 nesia ; and its presence is made known by the microscope in tissues in which 

 putrefaction has actively commenced, these being everywhere studded with 

 crystals of the " triple phosphate" of ammonia and magnesia, a salt which is 

 formed wherever phosphate of magnesia is dissolved in an ammoniacal liquid. 

 Phosphate of magnesia is introduced into the body as a part of the ordinary 

 food both of carnivorous and herbivorous animals ; but it exists in much larger 

 proportion in many vegetable substances, especially the seeds of the Cerealia, 



1 This statement is controverted by Von Bibra ; but it is supported by the analyses of 

 Lehmann and many other chemists. 



