18 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



ically superior to the ordinary fatty matter. The chief function of 

 lecithin is probably to serve for respiration; it represents the form into 

 which the fat must be changed to become combustible in the proto- 

 plasm, since the substances serving for respiration must be present 

 in the protoplasm in a dissolved condition/' Since fat is not soluble, a 

 transformation of it into soap was formerly assumed, a view which is 

 hardly possible in the case of plants, while upon animals soaps injected 

 subcutaneously exert a poisonous action (Munk, 1889). 



By the transformation of fatty matter into lecithin the higher fatty 

 acids are offered to the protoplasm in a soluble form, and after being 

 oxidized other molecules of fatty acids may enter into the place of the 

 former and thus the same molecules of the glycerol-phosphoric acid 

 can serve repeatedly as vehicles for oxidations of molecules of fatty 

 acids. The fact that blood corpuscles contain lecithin but not fat 

 seems to indicate that lecithin may be produced not only from fat, but 

 also directly from sugar, as is fat. A great therapeutic value of leci- 

 thin has been demonstrated in cases of nervous debility and weakness 

 of the alimentary functions. The brain and the whole nervous sys- 

 tem in general are rich in lecithin, fully 17 per cent of it having been 

 found in the gray substance of the brain. The nervous system requires 

 for its unceasing activity a substance which unites eas} r combustibility 

 with a great deal of potential energy in a small volume, which condi- 

 tions are admirably united in the lecithin. 



Seeds rich in starch generally contain much less lecithin than those 

 rich in protein. Thus, barley grains contain less than half the amount 

 contained in soy beans. The amount of lecithin increases to a certain 

 point in the first stages of germination, while the amount of fat 

 decreases. 5 Here the lecithin is evidently formed from the fat. It 

 seems very probable that the observed increase of lecithin is less than 

 was actually formed, since a part of it is probably consumed nearly as 

 quickly as produced. The evergreen tea leaves lose the reserve leci- 

 thin in spring (Hanai), and green plants generally lose it when kept in 

 the dark (Stoklasa). Heffter observed a decrease in the amount of 

 lecithin in the liver during starvation. E. Schulze ( found that during 

 germination the quantity of choline increases, and that in wheat the 

 choline is localized in the germ of the grain, but not in the endosperm. 

 This is certainhy of physiological interest, since the young developing 

 germ must carry on an energetic respiration and therefore be capable 

 of easily forming lecithin, in which process the presence of choline is 



a We can observe this with cholesterin, which is frequently contained in the cells 

 and, in fact, is, like lecithin, a constant concomitant of fatty matter. It is not per- 

 ceptibly oxidized by the protoplasm, the almost absolute insolubility in water being 

 here the obstacle. 



''Maxwell, Chem. Centralbl., Vol. XLI, No. 1, p. 365; Frankfurt, Landw. Vers. 

 Stat., Vol. XLIII. 



<■ Landw. Vers. Stat., Vol. XLVI. 



