oSob?ri9^2a''°'" }    Nature  of  the  Fat-Soluble  Vitamin.  729 
THE  NATURE  OF  THE  FAT-SOLUBLE  VITAMIN* 
The  discovery  of  the  dietary  importance  of  that  property  of 
many  foods  which  is  now  termed  fat-soluble  vitamin  or  fat-soluble 
A  represents  a  contribution  of  American  physiologists^  to  the  science 
of  nutrition.  It  has  been  repeatedly  verified  both  in  this  country 
and  abroad.  According  to  the  observations  made  on  a  variety  of 
experimental  animals,  the  lack  of  the  fat-soluble  vitamin  in  the  diet 
during  adolescence  may  lead  to  an  inhibition  of  growth  together 
with  symptoms  of  decline  in  health.  Most  conspicuous  in  a  specific 
way  is  the  apparently  increased  susceptibility  to  bacterial  infection. 
In  the  case  of  rats  this  lowered  resistance  first  betrays  itself  in  many 
instances  by  the  appearance  of  a  characteristic  disorder  of  the  ex- 
ternal eye  which  has  provisionally  been  classed  as  a  xerophthalmia. 
It  usually  begins  with  a  swelling  of  the  lids  which  is  followed  by  an 
inflamed  and  catarrhal  conditionof  the  conjunctiva.  This  rapidly 
becomes  worse,  and  the  discharge,  which  is  at  first  hemorrhagic, 
frequently  becomes  purulent.  If  untreated,  the  cornea  may  be- 
come involved  and  total  blindness  result.  If  a  food  containing 
fat-soluble  vitamin  is  administered,  the  symptoms  usually  clear  up 
in  a  few  days  without  further  treatment,  and  growth  is  resumed. 
The  same  phenomena  have  been  observed  in  mice,  and  more  recently 
in  rabbits  kept  on  diets  poor  in  the  fat-soluble  vitamin. ^  A  possible 
relation  of  the  lack  of  the  latter  to  the  occurrence  of  phosphatic 
calculi  has  also  been  pointed  out  by  Osborne  and  Mendel.^ 
Whether  and  in  what  manner  a  dietary  deficiency  in  fat-soluble 
vitamin  plays  a  part  in  human  disease  remains  to  be  ascertained. 
The  probability  of  the  need  of  this  food  accessory  in  the  ration  of 
man  is  large  and  the  possible  dire  effects  of  a  lack  of  it  are  being  dis- 
cussed widely  at  present,  notably  in  relation  to  the  pathogenesis 
of  pellagra,  rickets  and  xerophthalmia  in  childhood.  The  fact  that 
many  fats,  such  as  lard,  vegetable  oils  and  hydrogenated  fats,  which 
have  found  widespread  use  in  the  dietary  of  man  in  recent  years,  are 
*  From  the  Jour.  Amer.  Med.  Assoc.,  Aug.  21,  1920. 
1  McCollum,  E.  v.,  and  Davis,  M.:  /.  Biol.  Chem.,  15:  167,  1913;  Os- 
borne, T.  B.,  and  Mendel,  L.  B.,  Ibid.,  p'  311. 
2  Nelson,  V.  E.,  and  Lamb,  A.  R.:  "The  Effect  of  Vitamine  Deficiency  on 
Various  Species  of  Animals,  I.  The  Production  of  Xerophthalmia  in  the  Rab- 
bit," Am.  J.  Physiol.,  51;  530  (Apr.),  1920. 
3  Osborne,  T.  B.,  and  Mendel  L.  B.:  "The  Incidence  of  Phosphatic  Uri- 
nary Calculi  in  Rats  Fed  on  Experimental  Rations,"  J.  A.  M.  A.,  69:  32  (July 
7),  1917- 
