58 PHYSIOLOGY. 



as it forms a constituent part of the atmosphere. This, 

 however, is denied by some chemists. It is discharged from 

 the system in the same manner as oxygen, hydrogen, and 

 carbon ; though chiefly through the kidneys. 



8. Phosphorus exists both in animal and vegetable sub- 

 stances. Nearly every part of animal bodies contain it, 

 though it is found more abundantly in the bones. It gener- 

 ally exists in combination with oxygen, forming phosphoric 

 acid. It is discharged mostly through the kidneys. The 

 spontaneous combustion of human bodies, of which we have 

 some well-attested cases of drunkards, is supposed to be owing 

 to an accumulation of phosphorus in the system, from some 

 unknown cause. 



9./Sulphur is always united, in animal substances, with 

 other elements, as soda and potash. It is found in albumen, 

 in the hair and nails, and in muscular flesh. It is given off 

 by the intestines and by the skin. 



10. Chlorine is found in most of the animal fluids com- 

 bined with hydrogen. This forms hydrochloric acid. In 

 the blood it is combined with soda and potash. It is found 

 also in the gastric juice, in sweat, milk, saliva, &c. 



11. Potash exists more abundantly in plants than in ani- 

 mals. It is, however, contained in the blood, bile, urine, 

 sweat, milk, &c. 



12. Soda is more abundant in animals than plants. It 

 exists in the same fluids in which potash is found ; also in 

 bones and muscular flesh. It is always combined with some 

 acid. 



13. Lime forms a large part of the bones, in union with 

 phosphoric or carbonic acid. Silex exists in human hair, 

 and in some of the secretions. Magnesia is contained in 

 bones, and in some animal fluids, as milk. It is also found 

 in the brain. Iron forms the colouring principle of the red 

 globules of the blood, and is therefore pretty extensively 

 found in animal bodies. * 



