14 



al] the observations cited it will be seen tbat lecithin plays an impor- 

 tant role, and as its formation is made possible only when phosphoric 

 acid is present, one of the functions of this acid at once becomes intel- 

 ligible. 



PHOSPHORIC ACID IN CHLOROPHYLL. 



As Trecul, Gautier, and Hoppe have shown, the crystallized chloro- 

 phyllan also contains phosphoric acid (1.39 per cent) — indeed, for the 

 formation of the chlorophyll green the presence of phosphoric acid is 

 absolutely required (see p. 16). The opinion has been expressed that 

 the crystallized chlorophyllan is a kind of lecithin. While it is the 

 orthophosphoric acid that is contained in lecithin and chlorophyll, it is 

 the metapho sphoric acid which forms a constituent of the chromatin 

 (nuclein), as Leo Liebermann has discovered. 



POTASSIUM PHOSPHATE AS A CELL CONSTITUENT. 



That the secondary potassium phosphate as snch also has an impor- 

 tant physiological function becomes probable from its general occur- 

 rence in the living organisms. Relatively large proportions of it are 

 found in yeast cells, in the forming seeds, in the liver and muscles, 

 and in fact in all cases where special demands for great chemical 

 achievements are made. It causes the weak alkaline reaction of pro- 

 toplasm and is probably present in loose combination with certain 

 proteins, from which even treatment with water will often easily remove 

 most of it. 



The dry substance of muscles contains about 4 per cent of mineral 

 matter, of which again nearly two-thirds consist of dipotassium phos- 

 phate. This is also nearly the proportion found in beer yeast. Wheat 

 grains contain from 1 to 2 per cent ash, of which nearly one-half con- 

 sists of potassium phosphate and nearly one-fourth of calcium and 

 magnesium phosphate, while another portion of phosphoric acid present 

 in that ash corresponds to the destroyed nuclein and to the small por- 

 tion of lecithin.^ 



A further special function of phosphoric acid is the use of calcium 

 phosphate for the formation of bones. The blood ash of cattle contains 

 4 to 6 per cent and of man 9 to 11 per cent of phosphoric acid. The 

 requirements for normal field crops are considerable, a wheat crop, for 

 example, extracting from 1 hectare (about 2.5 acres) of ground about 

 26.5 kilos of this acid. The forest products require much less. It is in 

 the production of seeds especially that the powerful influence of fertil- 

 ization with phosphates becomes apparent. 



Whether hypophosphites, phosphites, or hypophosphates can ever be 

 of physiological value is a question which must be determined by 

 further studies. Knop showed in an experiment with maize in 1881 



I Several views have been expressed, as to the transportation of calcium phosphate 

 to the seeds. This salt is insoluble in water, but may be dissolved in small (luantities 

 by the weak acid juices of the plant. Vaudin (Chem. Zeit., No. 91, 1895) believes 

 that its transportation in the vegetable organism is accomplished by sugar and 

 potassium malate or citrate, which dissolve it in small quantities. 



