MINERAL CONSTITUENTS OF THE ANIMAL BODY. 405 



MINERAL CONSTITUENTS OF THE ANIMAL BODY. 



The chemistry of inorganic bodies has been so much more fully 

 investigated than that of organic substances, that it might naturally 

 be expected that our knowledge of the mineral constituents of vege- 

 table and animal bodies would far exceed that of the organic 

 constituents ; but, in truth, the reverse is the case, for we are far 

 less acquainted with these substances than with many organic 

 bodies. This circumstance is, however, not consequent on our 

 having paid less attention to the mineral constituents of organic 

 bodies, but is especially owing to the difficulty of separating these 

 substances, in an unchanged state, from organic matters, and of 

 ascertaining the conditions and combinations in which they actually 

 existed preformed in the organic substance. The fixed products 

 of the incineration or combustion of organic substances do not 

 afford us any information as to the combinations in which they 

 occurred in the organic substance. Nor can any reflecting chemist 

 for a moment suppose that the oxides and salts of the ash are con- 

 tained as such in the juices and tissues of living bodies. 



From a deficiency in the means of investigating or even of 

 conjecturing the true constitution of these substances in organic 

 parts, a higher value has been attached to the determinations of 

 the ash and its constituents than it merited, and the results of 

 these analyses have been more highly estimated than they deserve, 

 when we consider the agents cooperating in the incineration. It 

 has, moreover, frequently been forgotten that the quantity and 

 constitution of many of the constituents of the ash are in a great 

 measure dependent on the height of the temperature at which the 

 process of incineration was conducted ; that a great portion of the 

 substances has been volatilised by the simultaneous action of heat 

 and carbon ; and that the individual constituents of the ash have 

 entered into perfectly different combinations from what they had 

 done in the organic substance. 



We will here indicate only some few of the changes which the 

 mineral constituents of organic substances must necessarily undergo 

 when exposed to strong heat with a free admission of air. The 

 sulphur and phosphorus which were not contained in the organic 

 substance as sulphuric and phosphoric acids, must necessarily be 

 found in the ash as sulphuric and phosphoric acids combined with 



