730  Nature  of  the  Fat-Soluble  Vitamin.     { ^"'oc?obe?^r92'S: 
virtually  devoid  of  fat-soluble  vitamin  has  caused  some  concern 
owing  to  the  relatively  high  cost  of  those  fats,  like  milk  fat  and  egg 
fat,  which  are  rich  in  it.  It  is  a  relief  to  know,  however,  that  the  fat- 
soluble  vitamin  has  a  far  wider  distribution  in  nature  than  the  earlier 
studies  led  physiologists  to  suspect.  Only  recently  the  researches  of 
McCoUum,  Steenbock  and  their  collaborators  at  the  University  of 
Wisconsin,  ^  and  of  Osborne  and  MendeP  in  New  Haven,  have  indi- 
cated the  richness  of  many  sorts  of  plant  tissues  in  all  familiar  types 
of  vitamins,  thus  placing  the  dietary  importance  of  "vegetables"  in  a 
new  light. 
In  commenting  on  this  information,  Osborne  and  Mendel  re- 
mark that  it  emphasizes  the  use  of  vegetables  to  supplement  the  re- 
fined foods  of  the  modern  food  industry  which  furnishes  products 
rich  in  proteins,  fats  and  carbohydrates,  but  in  many  cases  com- 
paratively deficient  in  the  vitamins.  The  newly  acquired  facts,  they 
add,  serve  as  a  further  reminder  that  the  fat-soluble  vitamin  need  not 
be  sought  solely  in  foods  known  to  be  rich  in  fats.  Fat-soluble 
vitamin  has  never  been  isolated,  nor  has  it  been  concentrated  in  any 
way  which  avoids  the  simultaneous  presence  of  ordinary  fats,  to 
some  extent  at  least.  Although  its  reactions  and  behavior  toward 
solvents  suggest  a  lipoidal  character,  Steenbock  and  BoutwelP  have 
demonstrated  that  the  fat-soluble  vitamin  resists  saponification  with 
alkalis  whereby  true  fats  are  converted  into  soaps.  Hence  it  can 
scarcely  be  regarded  as  identical  with  fats.  This  fact,  for  which 
some  evidence  had  already  been  available,  represents  a  distinct 
step  in  advance  in  the  study  of  vitamins. 
The  extracts  containing  fat-soluble  vitamin  as  obtained  from 
natural  products  are  invariably  colored.  Yellow  corn  is  richer  in 
fat-soluble  vitamin  than  is  white  corn ;  there  is  a  similar  contrast  be- 
1  Steenbock,  H.,  and  Gross,  E.  G.:  "Fat-Soluble  Vitamine,  II.  The  Fat- 
Soluble  Content  of  Roots,  together  with  Some  Observations  on  Their  Water- 
Soluble  Vitamine  Content,"  /.  Biol  Chem.,  40:  501  (Dec),  1919;  "IV.  The  Fat- 
Soluble  Vitamine  Content  of  Green  Plant  Tissues,  together  with  Some  Obser- 
vations on  Their  Water-Soluble  Vitamine  Content,"  Ibid.,  41:  149  (Feb.),  1920; 
McCollum,  E.  v.:  "Newer  Knowledge  of  Nutrition,"  New  York,  19 19. 
2  Osborne,  T.  B.,  and  Mendel,  L.  B.:  "The  Vitamines  in  Green  Foods,"  /. 
Biol.  Chem.,  37:  187  (Jan.),  1919;  "Nutritive  Factors  in  Plant  Tissues,  IV.  Fat- 
Soluble  Vitamine,"  Ibid.,  41:  549  (Apr.),  1920. 
3  Steenbock,  H.,  and  Boutwell,  P.  W. :  "Fat-Soluble  Vitamine,  VI.  The  Ex- 
tractability  of  the  Fat-Soluble  Vitamine  from  Carrots,  Alfalfa,  and  Yellow 
Corn  by  Fat  Solvents,"  J.  Biol.  Chem.,  42:  131  (May),  1920. 
