INORGANIC FOODS. 403 



ently it bears about the same relation to calcium as potassium to sodium. 

 J. Malcolm 1 has shown that the introduction of soluble magnesium salts 

 into adult animals causes a loss of calcium. In growing animals it tends 

 to prevent the taking up of calcium. Soluble calcium salts apparently 

 have no effect upon the elimination of magnesium salts. In osteomalacia 

 we have also come to recognize a certain^ antagonism between these two 

 kinds of salts. 2 



Fluorine 3 likewise occurs in small amounts in milk, and forms a regular 

 constituent of bones and teeth, besides being found in the blood. 4 In 

 spite of the small amount present it cannot be disregarded. For this 

 element, as well as for all others, the Law of the Minimum holds. 



Phosphorus is of much greater importance both for the growing and 

 adult organism. We find phosphorus in the cells in the form of very 

 important compounds, namely lecithin, the nucleins and nucleoalbumins. 

 We know, furthermore, that phosphorus combined with the alkaline 

 earths forms one of the most important constituents of the human skele- 

 ton, and is also present in the same form in other tissues. Phosphorus is 

 present in milk, partly in organic combination, as in casein which belongs 

 to the group of nucleoalbumins, and partly as inorganic salt. Milk also 

 contains some lecithin. At present it is not known exactly how the 

 phosphorus is distributed between these different compounds in the 

 different kinds of milk. Apparently the amount of lecithin present is 

 not very large. 



There is no reasonable doubt that the living organism can utilize 

 phosphoric acid directly in the formation of lecithin. It is similarly 

 possible that it forms a part of its nucleins from the latter substance. 

 The fact that the animal organism can form lecithin from phosphates 

 without difficulty is apparent from the experiments already cited of 

 Miescher upon salmon. 5 



Phosphorus is especially important in the construction of nervous 

 tissue. The brain of a new-born infant weighs about 400 grams. This 

 weight is doubled during the period of lactation. According to Schloss- 

 mann's computations, 6 the nursling assimilates during this period for 

 the building up of its central nervous system alone about 0.75 gram of 

 phosphorus. The skeleton requires much more of this element. In 

 fact, if we estimate the total amount of phosphorus required by the infant 

 during the first year of its life, we shall find that it amounts to from 50 to 



1 J. Physiol. 32, 183 (1905). 



2 Cf. Lecture XVI, p. 377. 



3 G. Tammann: Z. physiol. Chem. 12, 325 (1888). S. Gabriel: ibid. 18, 281 (1894). 



4 J. Nickles: Compt. rend. 43, 885 (1886); Tammann: loc, cit. 



5 Cf. Lecture XVI, p. 351. 



6 Med. Klinik. No. 11 (1905); Arch. Kinderheilk. 40, 1. 



