[Proc. Eot. Soc. VicTOKiA, 23 (N.S.), Pt. II., 1911]. 



Art. XXX. — TJie Biocltemical Significance of 

 riiospliorihs. 



By HILDA KINCAID, M.Sc. 



(Government Eesearch Scholar, Physiological Laboratory, 

 University of Melbourne). 



[Read 10th November, 19101. 



The existence of plant life on the earth is essential for the 

 existence of animal life, since plants alone have the power 

 of living entirely on inorganic materials and of building them 

 into the organic substances necessary for the life of animals. 

 Plant life being thus essential, the chemical necessities of plants 

 will determine the chemical necessities of animals. 



Of the long list of known chemical elements only compara- 

 tively few are of any biological significance. The most im- 

 portant of those which are absolutely essential for plant and 

 therefore for animal life can be put into one or other of two 

 groups. 



1. The Water-borne or Soil elements, present in soil or 



dissolved in rivers or sea-water. To this group 

 belong sodium, potassium, magnesium, calcium, iron, 

 chlorine, sulphur and phosphorus. 



2. The Air-borne elements, present in air and in the case 



of oxygen and nitrogen usually in the free state. 

 To this group belong oxygen, hydrogen, niti'ogen 

 and carbon. Since these elements are air-borne 

 there will never be a serious deficiency of them ex- 

 cept in rainless areas. On the other hand there is 

 the possibility of deficiency in the soil elements. 

 Of the soil elements special interest is attached to phos- 

 phorus, not only on account of its presence in practically all 

 tissues both animal and vegetable, but also on account of the 

 fact that of all the elements necessary to life it is the one 

 in obtaining which difficulty may be encountered, since in order 

 to be used by the plant it must be in a form available to the 



