PHOSPHORIC ACID AND CELL DIVISION. 17 



solutions " with that of algae cultivated for eight weeks in solutions 

 free from phosphoric acid, but containing- all other necessary mineral 

 nutrients. The result was that there was no growth in the absence of 

 the phosphoric acid, but there was a yellow coloration of the chloro- 

 phyll and an accumulation of fat and albumin, while in the control 

 alga 3 the number of cells had more than doubled, the coloration of the 

 chlorophyll was normal, and the amount of fat and albumin stored up 

 was much smaller than in the former case. When, however, at the 

 end of eight weeks 0.1 per mille of monopotassium phosphate was 

 added to the culture free from phosphoric acid, a most energetic cell 

 division began in most of the cells after a short time, thus demonstrat- 

 ing the great importance of phosphoric acid for this purpose. 



A direct participation of inorganic phosphates in the formation of 

 albumin, as Liebig had assumed, has not been proved, and is improb- 

 able. As the writer has observed, cells of alga3 can continue to form 

 albumin for a certain length of time, even in the absence of inorganic 

 phosphates, although further growth and multiplication will be 

 stopped. 6 



THE PHYSIOLOGICAL IMPORTANCE OF LECITHIN. 



This ester of phosphoric acid contains fatty acids, glycerol, phos- 

 phoric acid, and choline, and corresponds to the following formula: 6 



0H 2 -O-(/) 



k-o-(/^ OH 



CH 2 — O— P = 



^O— (ch) 



It is a regular concomitant of fatty matter. It swells up in water and 

 is even somewhat soluble in it, a propert} T which renders it physiolog- 



«The composition of the solution made with distilled water for the control culture 



was as follows: 



Per mile. 



Potassium nitrate 0. 2 



Calcium nitrate 2 



Sodium sulphate 1 



Magnesium sulphate 1 



Monopotassium phosphate 1 



Ferrous sulphate Trace. 



The monopotassium phosphate was left out in one of the solutions. 



b Biol. Centralbl., 1891, Vol. IX, No. 9. 



c (/) Signifies the radical of a higher fatty acid; (ch) signifies the radical of 



choline: 



/CH3 



HO— CH 2 — CH— N— CH 3 



OH CH * 

 26982— No. 4:>— 03 2 



