220 LECTURE XII. 



vious lectures (pp. 160, 187) we regard the molecule of living 

 protoplasm as a very complex one, it is not improbable 

 that it contains fatty radicles, and that it may undergo 

 decomposition in such a way as to give rise to fats. On the 

 other hand, it has been found that fatty acids are among 

 the products of the artificial decomposition of proteid, and 

 it is therefore possible that fats may be formed in the living 

 cell by the decomposition of the dead proteid which it may 

 contain. In his researches upon the formation of fat in 

 Fungi, Naegeli made the important observation that this 

 process is dependent upon a supply of free oxygen. This 

 fact is, however, susceptible of various interpretations. It 

 may mean that, in the absence of free oxygen, the self- 

 decomposition of the living protoplasm does not take place, 

 and that therefore no fat is formed : or it may mean that, 

 under these conditions, the living protoplasm is incapable 

 of effecting the oxidative decomposition of the unorganised 

 proteid in such a way as to give rise to fat. We must be 

 content to leave this point undecided for the present. 



In any case the formation of fat is apparently not direct : 

 fatty acids first make their appearance, and these subsequently 

 combine with glycerin to form fats. Von Rechenberg has 

 found that unripe oily seeds contain a considerable quantity 

 of these acids, and that it gradually diminishes as the seeds 

 become mature. As to the glycerin of the fats, we are 

 unable at present to make any definite statement concerning 

 its mode of origin. 



Besides the fats (glycerides) already mentioned, other fatty bodies 

 have been found, in plants. These are, chlolesterin (CaeH^O), an alcohol 

 which has been found by Hoppe-Seyler and others in seeds, in buds, and 

 in yeast ; lecithin (C^HgoNPOg), a complex nitrogenous and phosphorised 

 fat, which has been found by Hoppe-Seyler to be widely distributed in 

 plants. Further, various fatty substances which are generally spoken of 

 as wax, are formed by plants: as these are to be rather regarded as 

 waste-products we shall treat of them subsequently. 



The nitrogenous plastic products are unorganised proteid 

 and amides. We have already discussed (p. 150) the possible 

 mode in which these bodies are formed synthetically in 



