FATS AND OILS, WAXES, AND LIPOIDS 145 



relation of colloidal phenomena to the activities of plant cell con- 

 tents has been more fully discussed (see Chapter XVI). 



Experimental studies of the physiological uses of lipoids have 

 thus far been devoted almost exclusively to those of animal tis- 

 sues. They have been seriously hampered by the difficulty of 

 securing properly purified extracts of lecithin and similar lipoids. 

 The same labile character which apparently makes them so 

 important in the chemical changes in the cell makes them equally 

 unstable compounds to work with hi attempting to secure pure 

 preparations for the purposes of experimental study. On this 

 account, there is, as yet, no certain knowledge concerning their 

 actual physiological uses. It is evident, however, that they 

 have some really important role to play, which opens up a prom- 

 ising field for further study. 



REFERENCES 



ABDERHALDEN, E. " Biochemisches Handlexikon, Band 3, Fette, Wachse, 

 Phosphatide, Cerebroside, . . . "340 pages, Berlin, 1911. 



HOPKINS, E. "The Oil-Chemist's Handbook," 72 pages, New York, 1902. 



LEATHES, J. B. "The Fats," 138 pages, Monographs on Biochemistry, Lon- 

 don, 1913. 



LEWKOWITSCH, J. "Chemical Technology and Analysis of Oils, Fats, and 

 Waxes," Vol. I, 542 pages, 54 figs.; Vol. II, 816 pages, 20 figs.; and Vol. 

 III., 406 pages, 28 figs., London, 1909. 



MACLEAN, H. "Lecithin and Allied Substances," 206 pages, Monographs on 

 Biochemistry, London, 1913. 



SOUTHCOMBE, J. E. "Chemistry of the Oil Industries," 204 pages, 13 figs., 

 London, 1918. 



