THE BIO-CHEMISTRY OF ANIMALS AND PLANTS 121 



or alkalies, and dates back to Hoppe-Seyler. He obtained the 

 first crystallised chorophyll derivative, which he called Chloro- 

 phyllan, by extracting grass with boiling alcohol. This substance, 

 according to him, is a lecithin derivative, in which the fatty acid 

 radicles are replaced by chromophoric groups of acid character. 

 These groups he called chlorophyllanic acids. The simplest 

 structural formula of it would be : 



CH 2 -0- radicle of chlorophyllanic acid. 

 CH-O- radicle of chlorophyllanic acid. 

 C H 2 — O - phosphoric acid - choline . 



It is, however, very doubtful if the constitution of the sub- 

 stance is so relatively simple. It always contains mineral 

 substances, especially magnesium, which seems to be an integral 

 constituent. 1 Schunck and Marchlewski considered it as mainly 

 composed of the two cleavage products, phyllocyanin and 

 phylloxanthin, whilst on the other hand Stoklasa could not 

 obtain crystallised chlorophyllan by Hoppe-Seyler's method. 

 He concludes, however, that the formation of chlorophyll is 

 intimately connected with the presence of phosphorus : " without 

 phosphorus no lecithin and also no chlorophyll." Willsttater 

 could only find relatively small amounts of phosphorus, and was 

 unable to obtain glycerin as a cleavage product. He isolated, 

 however, a nitrogen free alcohol, C 2 oH 40 0, and concludes that 

 chlorophyll is an ether, probably of this alcohol, with acids 

 which contain magnesium in a very resistant organic com- 



1 It was originally held that chlorophyll, like haemoglobin, was an iron com- 

 pound. This view was, however, completely disproved by later and more careful 

 investigation. The presence of iron seems always to be connected with oxidation 

 processes in the animal organism, whilst in the plant, especially in the assimilation 

 of carbonic acid by chlorophyll, we have to deal with a reducing process. In this 

 connection the presence of magnesium in chlorophyll is highly suggestive, and 

 another striking example of the necessity of magnesium for pigment formation is 

 furnished by the observation that the bacillus prodigiosus does not produce its 

 characteristic red pigment in the absence of magnesium salts. We always 

 associate a reducing action with this metal, and this function is perhaps the 

 explanation of its presence in the vital organs of the plant. The failure of 

 chemists to imitate nature in the reduction of carbonic acid to formaldehyde has 

 always been an argument against Baeyer's theory of formaldehyde formation as the 

 first intermediary assimilation product of plants. It is instructive to note that 

 Fenton, by using magnesium as the reducing agent, has succeeded where so 

 many have failed. 



