26 STRUCTURAL COMPOSITION OF HUMAN BODY. 



fluoride of calcium, it is deposited in minute granules, in a 

 peculiar compound, named bone-earth, containing 51.55 parts 

 of lime, arid 48.45 of phosphoric acid. Phosphate of calcium, 

 probably the neutral phosphate, is also found in the saliva, 

 milk, bile, and most other secretions, and acid phosphate in 

 the urine, and, according to Blondlot, in the gastric fluid. 



Magnesium appears to be always associated with calcium, 

 but its proportion is much smaller, except in the juice ex- 

 pressed from muscles, in the ashes of which magnesia prepon- 

 derates over lime. 



The especial place of iron is in the haemoglobin, the color- 

 ing-matter of the blood, of which a further account will be 

 given with the chemistry of the blood. Peroxide of iron is 

 found, in very small quantities, in the ashes of bones, muscles, 

 and many tissues, and in lymph and chyle, albumen of serum, 

 fibrin, bile, and other fluids ; and a salt of iron, probably a 

 phosphate, exists in considerable quantity in the hair, black 

 pigment, and other deeply colored epithelial or horny sub- 

 stances. 



Aluminium, Manganese, Copper, and Lead. It seems most 

 likely that in the human body, copper, manganesium, alumin- 

 ium, and lead are merely accidental elements, which, being 

 taken in minute quantities with the food, and not excreted at 

 once with the faeces, are absorbed and deposited in some tissue 

 or organ, of which, however, they form no necessary part. In 

 the same manner, arsenic, being absorbed, may be deposited 

 in the liver and other parts. 



CHAPTER III. 



STRUCTURAL COMPOSITION OF THE HUMAN BODY. 



IN the investigation of the structural composition of the 

 human body, it will be well to consider in the first place, what 

 are the simplest anatomical elements which enter into its for- 

 mation, and then proceed to examine those more complicated 

 tissues which are produced by their union. 



It may be premised, that in all the living parts of all living 

 things, animal and vegetable, there is invariably to be dis- 

 covered, entering into the formation of their anatomical ele- 

 ments, a greater or less amount of a substance, which, in 

 chemical composition and general characters, is indistiuguish- 



