434; NUTRITION ANIMAL HEAT AND FORCE. 



It differs in its uses so essentially from the chlorides, that they are hardly to 

 be compared. It is insoluble in water, but is held in solution in the fluids of 

 the body by virtue of free carbon dioxide, the bicarbonates and sodium chlo- 

 ride. In the solids and semi-solids, the condition of its existence is the same 

 as that of water ; L e. it is incorporated with the organic substance character- 

 istic of the tissue, is one of its essential constituents, and can not be com- 

 pletely separated without incineration. Nothing need be added here with 

 regard to this mode of union in the body, of organic and inorganic substances, 

 after what has been said with regard to water. 



The following table gives the relative quantities of calcium phosphate in 

 various situations : 



TABLE OF QUANTITIES OF CALCIUM PHOSPHATE. 



Parts per 1,030. 



In arterial blood. ( T> i A -\ t , -, ( 0'79 



i rogeriale and JVlarchal. 

 In venous blood. I ( 0-76 



In milk, human (Pfaff and Schwartz) 2-50 



In saliva (Wright) 0-60 



In urine, proportion to weight of ash (Fleitmann) 25-70 



In excrements (Berzelius) 40-00 



In bone (Lassaigne) 400-00 



In the vertebrae of a rachitic patient (Bostock) 136-00 



In teeth of an infant one day old . ~) f 510-00 



In teeth of the adult I . I 610-00 



In teeth, at eighty-one years ^ Lassaigne. ^ G6{HK) 



In the enamel of the teeth . . . 885-00 



By this table it is seen that calcium phosphate exists in very small quan- 

 tity in the fluids but is abundant in the solids. In the latter, the quantity 

 is in proportion to the hardness of the structure, the quantity in enamel, for 

 example, being more than twice that in bone. The variations in quantity 

 with age are very considerable. In the teeth of an infant one day old, Las- 

 saigne found 510 parts per 1,000 ; in the teeth of an adult, 610 parts ; and 

 in the teeth of an old man of eighty-one years, 660 parts. This increase in the 

 calcareous constituents of the bones, teeth etc., in old age is very marked ; 

 and in extreme old age they are deposited in considerable quantity in situa- 

 tions where there existed but a small proportion in adult life. The system 

 seems to gradually lose the property of appropriating to itself organic mat- 

 ters ; and although articles of food may be digested as well as ever, the power 

 of assimilation by the tissues is diminished. The bones become brittle, and 

 fractures, therefore, are common at this period of life, when dislocations are 

 almost unknown. Inasmuch as the efficiency of organs depends mainly upon 

 organic matters, the system actually wears out, and this progressive change 

 finally unfits certain parts for their various offices. An individual, if he 

 escape accidents and die of old age, passes away by a simple wearing out of 

 some essential part or parts of the organism. 



Uses of Calcium Phosphate. This substance, as before remarked, enters 

 largely into the constitution of the solids of the body. In the bones its office 

 is most apparent Its existence, in suitable proportion, is necessary to the 



