110 CHEMICAL COMPONENTS OF THE HUMAN BODY. 



nothing definite can be predicated of its uses. These are no doubt specially 

 connected with the function of the red-corpuscles, whatever this may prove to 

 be ; and it is an additional indication of the coloring-matter of the bile being 

 derived from haematin ( 70), to find that iron is readily detectable in the for- 

 mer substance. As almost every article of ordinary food, whether animal or 

 vegetable, contains iron, its presence in the system is easily accounted for. 

 Under ordinary circumstances, this source will be quite adequate; but when 

 there is a deficiency in the amount of the red-corpuscles of the blood, and it is 

 desirable to accelerate their production, the administration of iron in a separate 

 form, especially in conjunction with a diet of which animal flesh constitutes a 

 large part, usually promotes their development. 



88. The foregoing constitute all the inorganic substances (in addition to the 

 Sulphur and Phosphorus already spoken of in connection with the protein-com- 

 pounds), which can be regarded as normal components of the tissues and nutri- 

 tious fluids of the Human body. There are certain others, however, which 

 ordinarily present themselves in the excretions, either as constituents of the 

 food which are at once rejected, or as results of the chemical processes that take 

 place within the system ; and which, though occasionally to be detected in the 

 blood, seem to be present there only as on the road to their outlets. In this 

 light we are probably to regard the Alkaline Sulphates, which, although abun- 

 dant in the urine, are rarely to be detected in the blood, milk, bile, &c., except 

 by processes which will oxidize the sulphur they may contain, and which will 

 consequently produce sulphates that did not exist there before. Even when 

 sulphates are taken into the stomach, it appears that they are ordinarily con- 

 verted, in part at least, into sulphurets, in the alimentary canal ; this change 

 being due, as the experiments of Lehmann have shown, to the decomposition 

 which is going on in the organic matters in contact with the saline. Of that 

 which does not undergo this conversion, a small quantity finds its way into the 

 circulation, to be immediately eliminated by the kidneys; whilst the residue, if 

 large doses have been given, passes off unchanged in the feces. When no such 

 extraneous source of the sulphates exists in the solids or liquids ingested, the 

 quantity of them which is found in the urine may be considered as representing 

 an equivalent amount of sulphur which has been introduced into the system in 

 combination with the protein-compounds, and which has been set free and oxi- 

 dized in the final metamorphosis of tissue. The proportion is higher when a 

 strictly animal diet is employed, than when the diet is of the ordinary mixed 

 character; and higher on a mixed, than on a purely vegetable diet. This is just 

 what might be anticipated, from the larger proportion of the sulphurized com- 

 pounds in animal flesh. It appears scarcely requisite to mention Carbonate of 

 Magnesia under this head; since, although it is very commonly found in the 

 urine and in the urinary concretions of herbivorous animals, it is comparatively 

 rare in Man. As the magnesia seems to be introduced in the state of phosphate, 

 this carbonate is probably formed by double decomposition with some calcareous 

 salt formed by an organic acid, the lime being converted into a phosphate, and 

 the magnesia uniting with the organic acid, to be afterwards reduced to the state 

 of carbonate. Under this head may also be noticed the Sulphocyanide of po- 

 tassium which is usually present in human Saliva, and which gives a blood-red 

 color to the per-salts of iron, that is liable to be confounded with that produced 

 by morphia. As this substance occurs in extremely small quantity, and as it is 

 frequently absent altogether without any concurrent deficiency in the digestive 

 power, it cannot be regarded as an essential constituent of the Salivary secre- 

 tion. 



89. We have now, in the last place, to advert to the asserted presence of cer- 

 tain Metals, as normal or occasional constituents of the Human body. That 

 which is of the most importance in a medico-legal point of view, is Arsenic; 



