14 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



GENERAL VALUE OF CERTAIN MINERAL SALTS. 



Mineral salts have not only to perform physical as well as specific 

 chemical functions," but also seem to contribute directly to the main- 

 tenance of the living condition of the protoplasm. A most striking 

 instance of this is the rapid dying of infusoria in distilled water. The 

 writer entertained for a time the supposition that this phenomenon 

 might be due, as in the case of the alga Spirogyra, to slight traces of 

 copper sometimes found in distilled water and derived from the copper 

 vessels used in distilling. Experiments were therefore repeated, water 

 distilled from glass vessels being used, but the effect was the same — 

 the infusoria died with bloating, their protoplasm swelling and disin- 

 tegrating. The only conclusion that can be drawn, therefore, is that 

 the distilled water extracts from them traces of necessary constituents, 

 which must be mineral, since common water containing some mineral 

 matter has no such action, but forms the very medium of existence for 

 these organisms. A similar effect could not be observed with the same 

 distilled water on algae cells, which may remain alive in it for a consid- 

 erable time, although the growth ceases. But here the walls of the 

 cytoplasm are probably of greater density, which would prevent the 

 mineral matters of the cell from passing easily to the outside. 



This phenomenon observed in the case of infusoria strongly resem- 

 bles that of the red blood corpuscles and leucocytes, which are adapted 

 to the degree of concentration of the serum, and which die when trans- 

 ferred into distilled water, but remain alive for some time in a sodium- 

 chlorid solution of 0.6 per cent. The nature of the mineral salts 

 loosely bound by the proteids of the living matter may vary with the 

 character of these proteids. In the one case it may be sodium chlorid, 

 in another the secondaiy potassium phosphate, and in a third a calcium 

 salt. It should be pointed out once for all that we can hope to under- 

 stand the living state of protoplasm onUy when the proteins of the 

 living matter are recognized to be chemically labil bodies, which the 

 slightest influence often suffices to transform into the more stable 

 isomeric forms of dead matter. Relatively stable proteins are also 

 those in milk and the reserve proteins in eggs and seeds. Spon- 

 taneous transformations of labil compounds into stable ones b} r atomic 

 migration often take place very easily — for example, when certain 

 amido aldehydes or amido ketones are liberated from their combination 

 with acids. 



Years ago M. Xencki 6 recognized the importance of the mineral 



a Certain salts may also exert a stimulating action, that is, some fluorids, iodids, and 

 manganese and uranium compouuds, as has been shown by recent work of the writer 

 in conjunction with Messrs. Xagaoka, Aso, Sawa, and Suzuki. Great care must be 

 exercised in the use of such stimulants, since in certain amounts they act as poisons 

 rather than as stimulants. 



& Arch, des Sci. Biologiques de St. Petersburg, 1894, Vol. Ill, p. 312. 



