526 Creatin Content in Muscle [April-July 



posed. . . . Lipoids and ordinary fats, that is, lipins, occur in all 

 cells," etc. 



The proposed use of "lipins" has been gradually increasing, 

 evidently becaiise of the convenience of the term. We believe that 

 more general employment of this term would simphfy current dis- 

 ciissions of the fats and lipoids when mixtures of the two kinds of 

 materials are concerned and when neither " fats " nor " Hpoids " can 

 convey definitely more than the accepted meaning attached to the 

 term. To speak of fats as " Hpoids " is quite as absurd as to say 

 that starch is sidiXch-like substance. 



■ "Lipins" can be used as conveniently and more satisfactorily 

 than the term " fat," when " ether extract" or "solid matter in the 

 ether extract," is referred to in discussions of analytic results ob- 

 tained with the Soxhlet or other extraction methods. "Lipins" 

 certainly is a more suitable term than " Hpoids " when mixtures of 

 fats and Hpoids in or from tissues, ceHs, etc., are under discussion. 

 The simple derivative, " delipinize," which we have been using 

 freely, is far more convenient^ than the phrase " remove the fat, 

 lipoids and similarly soliihle substances"; it is also a good Substi- 

 tute in chemical terminology for the less technical though nearly 

 obsolete term " degrease" ("to remove the grease from"). In 

 the terminology pertaining to enzymes, " lipases " accords perfectly 

 with " lipins" the former generic term applying to enzymes capable 

 of transforming one or more "lipins." "Lipolytic," " lipoclastic," 

 "lipotropic," etc., would relate logically to such "lipins" as lecithin, 

 quite as satisfactorily as to " lipins " Hke tributyrin. 



Until we learn "everything" about the physics and chemistry of 

 all the fats, lipoids and other fat-like materials, we shall be unable, 

 obviously, to select terms that will exactly, completely and finally 

 classify these substances on a strictly chemical basis. Meanwhile, 

 "lipins" will be a general convenience — a term that can easily be 

 rejected when its serviceability ends. 



The creatin content in muscle, its quantitative relation to the 

 total muscle substance, to the body in general, and to factors which 



2 Bronfenbrenner and Rockman; Biochemical Bulletin, 1914, iii, p. 375. 



