A monograph on lecithin in which the above subject is reviewed, 

 with a complete list of references, by Maclean (1918) has recently been 

 published. 



The first plant nucleic acid was discovered by Altmann (1889) 

 as a constituent of yeast cells. This substance was similar to nucleic 

 acids isolated from animal tissues, but it showed certain differences in 

 composition, particularly in cleavage products (Kossel 1891, 1893, 

 1894). Osborne and Harris (1902) described the triticonucleic acid 

 obtained from wheat embryo. This substance was found to be similar 

 to yeast nucleic acid and the identity of the two acids was established 

 by the investigations of Levene and La Forge (1910). It appears, 

 therefore, that there is only one plant nucleic acid. This substance 

 has been very extensively investigated by Levene, Levene and Jacobs 

 and more recently by Jones and Read (1917). The structure of plant 

 or yeast nucleic acid has not yet been fully established. It has been 

 shown, however, by Levene and Levene and Jacobs that the molecule 

 of yeast nucleic acid contains four nucleotides which are made up of 

 the following constituents : 



Phosphoric acid — d — ribose — guanine 

 Phosphoric acid — d • — ribose — cytosine 

 Phosphoric acid — d — ribose — uracil 

 Phosphoric acid — d — ribose • — adenine 

 This subject is extensively reviewed in the monograph by Jones 

 (1914), "Nucleic Acids: Their Chemical Properties and Physiological 

 Conduct." 



The observation that fermentation is accelerated by the addition 

 of phosphates was first made by Wroblewski (1901) and later by 

 Buchner and Hahn (1903). Studies made since that time have shown 

 that during fermentation inorganic phosphate disappears and that an 

 organic phosphoric acid is produced. Phosphates are apparently essen- 

 tial in the process of fermentation and in the absence of phosphates no 

 fermentation can take place (Harden 1914). The nature of the organic 

 phosphoric acid and the conditions under which it is formed have been 

 studied by Harden and Young (1905, 1908, 1909, 1911), by Iwanoff 

 (1905, 1909), Young (1909, 1911), Lebedeff (1909, 1910. 1911, 1912, 

 1913) and by Euler (1912) and his students (1911, 1912). 



There is no complete agreement among these investigators as to 

 the constitution of this organic phosphoric acid. Iwanoff regards it 

 as a triosemonophosphoric acid, C 3 H 5 2 (P0 4 H 2 ), while Harden and 

 Young believe that it is a hexosediphosphoric acid, C 6 H 10 O 4 (P0 4 H 2 ) 2 . 

 Euler believes tha.t a mixture of these two acids is formed during fer- 

 mentation. For further particulars regarding this interesting phos- 

 phoric acid, reference is made to the monograph by Harden (1914). 

 Another interesting substance, the phosphoric acid of starch, has 



