512  Stability  of  Vitamins.  { Km-jl°yT\g^Tm' 
amounts  and  are  not,  by  themselves,  able  to  support  growth.  Lloyd,3 
in  England,  has  called  attention  to  the  alleged  role  of  vitamins  in  the 
growth  of  the  meningococcus,  concluding  from  her  investigations 
that  the  primary  cultivation  of  this  microorganism  in  vitro  is  possible 
only  in  the  presence  of  certain  accessory  growth  factors  present  in 
blood,  serum,  milk  and  other  animal  fluids,  and  probably  also  in 
vegetable  tissues.  She  regards  the  essential  substances  as  mod- 
erately stable  toward  heat.  In  this  country,  Davis4  has  offered 
further  evidence  that  something  comparable  with  vitamin  phenomena 
may  appear  in  bacterial  nutrition.  His  attention  has  been  directed  to 
the  growth  of  hemophilic  bacteria  which  require  hemoglobin  for 
their  development.  For  optimal  growth,  however,  something  more 
seems  to  be  essential,  and  the  added  factor,  not  found  in  synthetic 
mediums,  is  found  in  foreign  bacteria,  and  in  fresh  animal  and  plant 
tissues.  How  the  substances  thus  furnished  act  is  quite  as  obscure 
as  is  the  answer  to  the  question  of  their  chemical  nature.  Davis  sug- 
gests that  they  may  function,  in  the  case  of  hemophilic  bacilli,  to 
render  iron  more  available ;  and  he  ventures  the  further  suggestion 
that  the  action  of  vitamins  in  animals  and  higher  plants  may  concern 
or  somehow  control  the  metabolism  of  certain  elements  like  iron, 
phosphorus,  calcium  or  iodine,  as  well  as  possibly  the  protein  metab- 
olism. It  is  perhaps  too  early  in  the  period  of  collecting  facts  in 
this  field  of  study  and  critically  evaluating  them  to  indulge  in  elab- 
orate hypotheses  ;  but  the  fascinating  mystery  of  the  vitamins  is  pene- 
trating into  many  avenues  of  biologic  inquiry.  Science  must  guard 
against  undue  enthusiasm  when  so  much  uncertainty  and  contradic- 
tion still  exist. 
THE  STABILITY  OF  VITAMINS.1 
There  is  a  widespread  impression  that  those  as  yet  little  under- 
stood, but  apparently  indispensable,  components  of  the  diet  popularly 
termed  vitamins  are  easily  destroyed  by  heat.  Obviously  the  estab- 
lishment of  the  truth  in  this  respect  is  a  matter  of  great  importance. 
Most  of  the  foods  that  enter  the  diet  of  man  beyond  the  period  of  in- 
3  Lloyd,  Dorothy,  Jour.  Path,  and  Bacteriol.,  1916,  21,  113. 
4  Davis,  D.  J.,  "Food  Accessory  Factors  (Vitamins)  in  Bacterial  Culture, 
with  Especial  Reference  to  Hemophilic  Bacilli,"  I,  Jour.  Infect.  Dis.,  1917, 
21,  392. 
1  From  the  Journal  of  the  American  Medical  Association,  April  27,  1918 
