iQii] Jacob Rosenhloom and Williarn J. Gies 53 



II. Natural carbocyclic lipins 



A. STEROLS. Natural terpeno-alcoholic derivatives. All of these sub- 



stances contain carbon, hydrogen and oxygen, but they are free from 

 phosphorus, sulfur and nitrogen. They resist saponification (" non-saponi- 

 fiable fat"), but form esters (Group II, B). Leading members of the 

 group are cholesterol, iso-cholesterol, koprosterol and sitosterol. These 

 substances are Abderhalden's "Sterins" and, with the conjugate lipins 

 (Group I, B), constitute the group of socalled "lipoids." 



B. ESTEROLS. Natural terpeno-aliphatic waxes ; soap-yielding sterol esters 



(Group II, A), such as cholesteryl palmitate in lanolin and cholesteryl 

 oleate in blood. 



C. CHOLATES. Terpeno-cfc;'c? derivatives of hepatic origin, probably from 



sterols or sterol radicals (page 56). 



a. Cholic acids (and their simple biological salts), such as cholic acid and 



choleic acid. 



b. BiLE ACIDS (and their biological salts), such as glycochoHc acid and 



taurocholic acid. 



III. Natural lipins of undetermined Constitution 



A. CHROMOLIPINS. Pigments which cannot be saponified and which are 



comparatively unaffected tinctorially by caustic alkali, such as lipo- 

 chromes. 



B. MISCELLANEOUS LIPINS. Substances of uncertain qualities or doubt- 



ful existence, such as krinosin and bregenin. 



IV, Artificial lipins 



Many laboratory products such as tri-acetin, lead oleate, cholesterol benzoate, 

 sodium cholesterylate, strychnin-lecithate, stearyl alanate, creatin-lecithate, 

 and potassium-kephalate. 



The foregoing general Classification is wide open for improvement. Its 

 adaptability to change in harmony with new chemical discoveries is ap- 

 parent. We expect to present a detailed extension of it in the near 

 future. 



IL IS CHOLESTEROL THE MOTHER SUBSTANCE OF CHOLIC 

 ACID AND THE BILE SALTS? 



During the development of the accompanying Classification of 

 the lipins, the senior author issued the following comment in his 

 mimeographed directions for the laboratory work of the course 

 in physiological chemistry required of first year stiidents of medi- 

 cine at this University (1909-1910) : 



" 470. Physical and chemical properties of cholesterols. — The 

 methods employed in these experiments for the isolation of choles- 



