INOKGANIC PKINCIPLES. 495 



Table of Quantities of Phosphate of Lime. 



Parts per 1,000. 



In Arterial blood, ) pialeandMarcha] < 0*79 



" Venous blood, f \ 0*76 



" Milk, human (Pfaff and Schwartz) 2*50 



" Saliva (Wright) 0*60 



" Urine, proportion to weight of ash (Fleitmann) 25*70 



" Excrements (Berzeiius) 40*00 



" Bone (Lassaigne) 400'00 



" Vertebra of a rachitic patient (Bostock) 136*00 



" Teeth of an infant one day old ^ ( 510-00 



" Teeth of adult I . I 610-00 



<- Teeth, at eighty-one years. . | 1 660*00 



" Enamel of the teeth J I 885*00 



By this table it is seen that the phosphate of lime exists in very small quantity 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 being, for example, more than twice 

 that in bone. The variations in quantity with age are very considerable. In the teeth 

 of an infant one day old, Lassaigne 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 elements of the bones, teeth, etc., in old age is very marked; and in 

 extreme old age they are deposited in considerable quantity in situations where there 

 existed but a small proportion in adult life. The system seems to gradually lose the 

 property of appropriating to itself organic matters ; and, although articles of food are 

 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 disloca- 

 tions are almost unknown. Inasmuch as the real efficiency of organs depends upon organic 

 matters, the system actually wears out, and this progressive change finally unfits the 

 various parts for the performance of their functions. An individual, if he escape acci- 

 dents and die, as we term it, of old age, passes away thus by a simple wearing out of his 

 organism. 



Function of Phosphate of Lime. This substance, as before remarked, enters largely 

 into the constitution of the solids of the body. In the bones its function is most appar- 

 ent. Its existence, in suitable proportion, is necessary to the mechanical office of these 

 parts, giving them their power of resistance, without rendering them too brittle. It is 

 more abundant in the bones of the lower extremities, which have to sustain the weight 

 of the body, than in those of the upper extremities ; and in the ribs, which are elastic 

 rather than resisting, it exists in less quantity than in the bones of the arm. 



The necessity of a proper proportion of phosphate of lime in the bones is made evi- 

 dent by cases of disease. In rachitis, where, as is seen by the table, its quantity is very 

 much diminished, the bones are unable to sustain the weight of the body, and they become 

 deformed ; and finally, when the phosphate of lime is deposited, they retain their distorted 

 shape. The phosphate of lime may be extracted from the bones by maceration in dilute 

 hydrochloric acid, which dissolves it, leaving only the organic substance. Bones treated 

 in this way, although they retain their form, become very pliable ; and a long slender 

 bone, like the fibula, may be actually tied into a knot. 



Origin and Discharge of Phosphate of Lime. The origin of this principle is exclu- 

 sively from the external world. It enters into the constitution of our food and is dis- 

 charged in the faeces, urine, and other matters thrown off by the body. Its quantity 

 in the urine is exceedingly variable. Lecanu found from 0'437 to 29*250 grains thrown 

 off by the kidneys during the twenty-four hours. 



Carbonate of Lime. This principle exists in the bones, teeth, cartilage, internal ear, 



