§1J 



UPON THE RATE OF GROWTH 



303 



TABLE XXXII 

 Comparison of Ash in New-boen Dog and in the Milk of its Mother 



The quantities in the two columns are fairly similar. The 

 greatest proportional difference occurs in the case of iron, and 

 this fact requires a special explanation, which is briefly this, 

 that iron is more important for the rapidly growing embryonic 

 stages than for later life. 



So likewise in the eggs of birds we find stored up all the 

 mineral matters which are necessary for their development. 

 Thus the yoke of the hen's &g'g contains phosphoric acid, lime, 

 ■chlorine, potassa, soda, magnesia, iron oxide, and silica in the 

 relative abundance indicated in this descending series. This 

 series closely agrees with that given for milk. 



In the case of marine animals, also, certain inorganic elements 

 are a necessary food. The following list of such elements is 

 l)ased upon the results of thorough experiments by Hekbst 

 ('97) upon developing eggs of sea-urchins, starfishes, hydroids, 

 ■ctenophores, and tunicates ; the most favorable proportions of 

 the elements were not, however, determined : calcium (in the 

 form of carbonate, sulphate, or chloride), chlorine, iron (trace), 

 magnesium, phosphorus (as CagP.^Og or CaHPO^), potassium, 

 sodium, and sulphur. Now all these elements are found in sea 

 water, which in the Mediterranean Sea near Naples contains in 

 1000 parts of water * 



* After FoKCHHAMMEK ('61), p. 383. 



