412 FIRST CLASS OF MINERAL CONSTITUENTS. 



1. Those which are of especial use in the animal body through 

 their physical properties. 



2. Those which are adapted by their chemical properties to 

 serve definite objects in the animal economy : and 



3. Those which are only incidentally conveyed into the animal 

 body, exert no influence on any special process, and are, therefore, 

 speedily eliminated from the organism. 



FIRST CLASS OF MINERAL BODIES. 



WATER. 



It would be superfluous to enumerate the uses of this substance 

 in the animal organism ; we will confine ourselves to the two simple 

 remarks that water is essential to the establishment of all chemical 

 activity, and, further, that the functions, or rather the physical 

 properties, of certain tissues, are dependent on the presence of a 

 certain quantity of water which is merely in a state of mechanical 

 combination. 



PHOSPHATE OF LIME. 



This is the most important of all the mineral substances which, 

 by their physical properties, are of service in the animal body. 

 The use of its presence in the bones, where it gives solidity and 

 strength to the osseous skeleton, is at once apparent. Bones 

 deficient in this salt are proportionally deficient in firmness: thus 

 we observe that softening of the bones occurs in those conditions 

 when the animal organism does not receive a sufficient supply of 

 phosphate of lime, or when certain physiological processes require 

 an increased consumption of this salt, as in pregnancy, and 

 during the dentition of children. We need hardly remark that 

 rachitis frequently, if not always, occurs simultaneously with the 

 period of dentition, that the consumption of phosphate of lime 

 during pregnancy is often so great that scarcely any traces of it 

 can be found in the urine, and that during this period of woman's 

 life fractures unite with extreme difficulty, and sometimes do not 



