﻿ORGANISM 
  AND 
  MECHANISM 
  113 
  

  

  it 
  is 
  important 
  to 
  notice 
  that 
  the 
  working 
  out 
  of 
  the 
  cheinico- 
  

   physical 
  description 
  of 
  vital 
  activity 
  is 
  not 
  altogether 
  plain 
  

   sailing. 
  Let 
  us 
  illustrate. 
  

  

  3. 
  Some 
  Difficulties 
  in 
  the 
  Application 
  of 
  Physical 
  and 
  

   Chemical 
  Formulas 
  to 
  Organisms. 
  

  

  It 
  is 
  a 
  general 
  fact 
  of 
  experience 
  that 
  the 
  rate 
  of 
  chemical 
  

   reactions 
  is 
  accelerated 
  by 
  heat 
  and 
  retarded 
  by 
  cold. 
  The 
  

   illustrious 
  chemist 
  Van't 
  Hoff 
  formulated 
  the 
  law 
  that 
  the 
  

   rate 
  of 
  a 
  chemical 
  process 
  increases 
  in 
  geometric 
  progres- 
  

   sion 
  when 
  the 
  temperature 
  is 
  increased 
  in 
  algebraic 
  progres- 
  

   sion. 
  The 
  velocity 
  of 
  the 
  reaction 
  may 
  be 
  doubled 
  or 
  trebled 
  

   by 
  a 
  rise 
  in 
  temperature 
  of 
  10 
  C. 
  or 
  reduced 
  by 
  one-half 
  

   or 
  more 
  by 
  a 
  fall 
  in 
  temperature 
  of 
  10 
  C. 
  Now 
  it 
  has 
  been 
  

   observed 
  that 
  the 
  rate 
  of 
  heart-beat 
  of 
  various 
  animals, 
  so 
  

   widely 
  separated 
  as 
  tortoise 
  and 
  water-flea, 
  is 
  reduced 
  to 
  

   about 
  a 
  half 
  if 
  the 
  temperature 
  be 
  lowered 
  10 
  C., 
  and 
  the 
  

   same 
  holds 
  of 
  some 
  other 
  vital 
  processes. 
  Therefore 
  it 
  has 
  

   been 
  hastily 
  concluded 
  that 
  the 
  chemical 
  processes 
  associ- 
  

   ated 
  with 
  vital 
  activities 
  follow 
  Van't 
  Hoff's 
  law 
  in 
  the 
  way 
  

   they 
  vary 
  in 
  rate 
  with 
  changes 
  in 
  temperature. 
  But 
  it 
  

   looks 
  as 
  if 
  the 
  conclusion 
  had 
  been 
  premature. 
  The 
  increase 
  

   in 
  the 
  rate 
  of 
  development 
  of 
  the 
  eggs 
  of 
  the 
  plaice 
  is 
  

   directly 
  proportional 
  to 
  the 
  increase 
  in 
  the 
  temperature 
  

   within 
  the 
  limits 
  of 
  viability 
  (Dannevig, 
  Johansen, 
  Krogh) 
  ; 
  

   it 
  does 
  not 
  illustrate 
  Van't 
  Hoff's 
  law. 
  In 
  certain 
  fishes, 
  in 
  

   frogs, 
  water-beetles, 
  and 
  sea-urchins 
  the 
  Danish 
  physiologist 
  

   Krogh 
  finds 
  that 
  the 
  relation 
  between 
  the 
  temperature 
  and 
  

   the 
  rate 
  of 
  development 
  cannot 
  be 
  expressed, 
  even 
  approxi- 
  

   mately, 
  by 
  Van't 
  Hoff's 
  formula. 
  According 
  to 
  Krogh's 
  ex- 
  

   periments 
  on 
  frogs 
  and 
  goldfishes 
  and 
  some 
  other 
  animals, 
  

   the 
  influence 
  of 
  temperature 
  on 
  the 
  t 
  standard 
  ' 
  metabolism, 
  

  

  