OF VITAL PHENOMENA 187 



A few protective solutions have the following percentage com- 



position : 



2 8 Q § 3 ? 3 



Q r Q o ffi K a 



Q hd nj 



P O p 



{Ringer's (frag) .65 .014 .012 — .02 .001 



Gothlin's " .65 .01 .0065 — .1 .008 .009 



Locke's (mammal) .9 .042 .024 — .01-.03 



Tyrode's .8 .02 .02 .01 .1 .005 



'Piihner's (sharks) 2.0 .01 .02 .02 2.5 



The above solutions may be made nutritive by the addition of 

 .1-.25 per cent glucose. 



Many green plants will live in distilled water and need no 

 especially protective solution except that any ion if in very high 

 concentration must be made harmless by the presence of some 

 antagonistic ion. Knop's solution is protective and nutritive for 

 green plants. It is made by dissolving the following numbers 

 of grams in 3-7 liters of water: 4 Ca(N0 3 ) 2 , 1 KN0 3) 

 1 KH 2 P0 4 , 0.5 KC1, 1 (MgS0 4 -7H 2 0). It is probable that 

 traces of impurities in this solution are essential since many 

 plants contain additional elements. The analyses of Jost on the 

 ash of a number of land plants show them to contain the fol- 

 lowing minerals, beginning with the most abundant: CaHP0. 1; 

 K, Mg, Mn, Na 2 S0 4 , Si, CI, Fe. The P and S entered at least 

 partly into the composition of proteins, but since anions are 

 necessary to combine with the cations, the salts were probably 

 phosphates, sulphates, chlorides and carbonates. 



According to Stoklasa (1908) the ash of Azobacter is almost 

 pure K 2 HP0 4 . Ad. Mayer (1902) used the following solution 

 for the growth of yeast, expressed as grams dissolved in two 

 liters: 1 KH 2 PO„ 0.1 Ca 3 (P0 4 ) 2 , 1 MgS0 4 . 



Salts of As, Or, Zn, Cd, Ni, Co, Cu, Hg, Au and Pt are said 

 to stimulate the growth and fermentative activity of certain 

 fungi, when in certain minute concentrations. These salts are 

 probably to be considered protective (affecting permeability), 

 since the heavy metal ions are powerful antagonists to some more 

 common cations, and only this antagonistic action explains the 

 necessity of exactly limiting the concentration of the heavy metal. 



Bacteriological media are too numerous to be considered here. 

 The PH is very important (see papers of W. M. Clark). 



