IRON. 443 



beautiful views which Liebig, with his customary skill, has de- 

 veloped in his classical memoir on this subject. He has there par- 

 ticularly directed attention to the different proportions in which 

 potash and soda exist in the blood and in the muscular fluid ; this 

 very important difference is less marked in Rose's analyses of the 

 mineral constituents of both fluids, and taking into consideration 

 the importance of the subject, it is exceedingly necessary, in order 

 that we should have a clear insight into these relations, that we 

 should form a decisive opinion regarding the value of the facts in 

 our possession. 



A glance at the numerous analyses of the ashes of plants, and 

 especially of their seeds, is sufficient to indicate the source of the 

 phosphates in the animal body ; the copious discharge of phos- 

 phates by the urine need scarcely excite our wonder, as it 

 includes both those which were contained preformed in the food, 

 and those which are formed during the metamorphosis of animal 

 tissue, by the oxidation of the phosphuretted organic matters or 

 radicals. 



IRON. 



This metal occurs in the animal body, not only in very dif- 

 ferent parts, but also in different conditions ; in the blood, as we 

 have already shown in our observations on hcematin, it seems 

 highly probable that it exists, for the most part, in a non-oxidised 

 state ; in the gastric juice it exists, according to Berzelius, as a 

 protochloride, and in other fluids as a phosphate. 



According to Rose's method, the ash of ox-blood contains 6'84g 

 of peroxide of iron, that of horse-flesh 1*00^, that of milk 0*47 8, 

 that of the yolk of egg 1.85%, that of the white of egg 2'09f , that 

 of the bile 0-23 % and that of the faeces 2'09f . We have already 

 noticed the presence of iron in black pigment in our remarks on 

 melanin. Large quantities of iron are sometimes found in the 

 ashes of gall-stones, especially of such as consist chiefly of pigment. 

 There appears to be no relation between the colour of the hair, 

 and the quality of the iron which it contains. (Lae'r.*) 



We are unfortunately perfectly ignorant regarding the special 

 uses of iron in the animal economy. In reference to the iron in the 

 blood, we have already seen (p. 308) that it is in some way con- 

 nected with the function of the corpuscles, but we know nothing 

 * Ann. d, Ch. \i. Pkarm. Bd. 45, S. 227. 



