134 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



urine of the herbivora but little calcium phosphate is present, and this is 

 not dissolved, but merely suspended, and readily deposits as a sediment. 

 In the solid tissues the lime phosphate appears to be simply deposited in 

 the interstices of the .organic bases, and it may be removed as, for 

 example, from bone by prolonged maceration in dilute hydrochloric 

 acid, without altering the form of the bone. As Dalton says : " In the 

 bones, teeth, and cartilage 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 character 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 macer- 

 ation in dilute muriatic acid, leaving behind the animal substance, which 

 still retains the original form of the bone or cartilage." The bone so 

 treated preserves its outline perfectl}', but has entirely lost all rigidity, 

 and may be twisted up, and the long bones may often be tied into a knot. 

 Calcium phosphate, therefore, gives to bone-tissue its rigidit}^ Conse- 

 quentl} T when, either through some faulty process in the organism or 

 through the deprivation of calcium salts from the food, this substance is 

 not deposited in normal amounts in the bones, the latter become soft, 

 flexible, and deformed, forming the affection known as rachitis ; or, in 

 adult life, a similar morbid softening of bones may take place from 

 a defective deposit of calcareous matter, and a progressive yielding of 

 the bony skeleton takes place, constituting the disease known as osteo- 

 malacia. 



The greater part of the calcium phosphate enters the body in the 

 food, being contained in both animal and vegetable articles of diet. In 

 suckling animals the milk contains, in its normal condition, a sufficient 

 amount of calcium phosphate to supply the growing organism with its 

 requisite quantity. When taken in vegetable food, where, of course, it 

 is ordinarily present as a union of calcium with one or more of the 

 organic acids, in the animal body, as already referred to, it undergoes 

 decomposition into calcium phosphate and carbonates of the alkalies. 



9. MAGNESIUM PHOSPHATE (2(P0 4 )Mg 8 , 2(P0 4 )MgH 4 ). Like cal- 

 cium phosphate, magnesium phosphate is found in all the tissues and 

 fluids of the animal body, though in far smaller amount, with the excep- 

 tion of muscle and the thymus gland, where the magnesium phosphate 

 is in excess. The bones of the herbivora contain more magnesium phos- 



