MINERAL SUBSTANCES IN ANIMAL BODIES, 13* 



CHAPTER XI. 



On the Rotation of Crops. 



It has been shown, by accurate examinations of animal bodies, 

 that the blood, bones, hair, &c, as well as all the organs, contain 

 a certain quantity of mineral substances, without the presence of 

 which in the food, these tissues could not be formed. 



Blood contains potash and soda in combination with phosphoric 

 acid ; the bile is rich in alkalies and sulphur ; the substance of 

 the muscles contains a certain amount of sulphur ; the blood 

 globules contain iron ; the principal ingredient of bones is phos- 

 phate of lime ; nervous and cerebral substance contains phos- 

 phoric acid and alkaline phosphates ; and the gastric juice 

 contains free muriatic acid. 



We know that the free muriatic acid of the gastric juice and 

 part of the soda of the bile is obtained from common salt ; 

 and we are enabled, by the mere exclusion of this material 

 from food, to put an end to the digestive process and life of an 

 animal. 



When a young pigeon is fed upon grains of wheat in which 

 phosphate of lime, the principal constituent of the bones, is defi- 

 cient, and when it is prevented receiving this substance from 

 other sources, its bones become thin and friable, and death ensues 

 if the supply of this mineral substance is still prevented. 

 (Choiset, Report to the Academy of Paris, June, 1842.) In 

 like manner, if we exclude carbonate of lime from the food of 

 fowls, they lay eggs without the hard exterior shell. 



When a cow is fed upon an excess of roots, such as potatoes 

 and turnips, the same thing must happen to it, as in the case of 

 the pigeon cited above ; for these roots contain phosphate of 

 magnesia, and only traces of lime. Now, if we remove daily 

 from the same cow a certain amount of phosphate of lime in its 



