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  PROCEEDINGS 
  OF 
  THE 
  CALIFORNIA 
  

  

  These 
  substances 
  all 
  belong 
  to 
  the 
  same 
  isomorphons 
  group, 
  their 
  distinctive 
  

   physiological 
  action 
  being 
  that 
  they 
  are 
  all 
  lung 
  poisons, 
  as 
  they 
  kill 
  by 
  the 
  ac- 
  

   tion 
  they 
  exert 
  on 
  the 
  lungs, 
  either 
  by 
  suddenly 
  arresting 
  the 
  pulmonary 
  circu- 
  

   lation 
  or 
  by 
  causing 
  changes 
  in 
  the 
  lung 
  tissue 
  which 
  prevent 
  the 
  aeration 
  of 
  the 
  

   blood. 
  Having 
  experimentally 
  investigated 
  the 
  physiological 
  action 
  of 
  most 
  of 
  

   the 
  more 
  important 
  groups 
  of 
  inorganic 
  compounds, 
  comprising 
  about 
  forty 
  of 
  

   the 
  different 
  elements, 
  I 
  would 
  l)ring 
  forward 
  a 
  large 
  amount 
  of 
  evidence, 
  show- 
  

   ing 
  that 
  to 
  a 
  certain 
  extent 
  a 
  connection 
  exists 
  -between 
  the 
  relative 
  atomic 
  

   weight 
  of 
  substances 
  in 
  the 
  same 
  isomorphous 
  group 
  and 
  their 
  physiological 
  ac- 
  

   tion, 
  and 
  this 
  I 
  propose 
  to 
  do 
  on 
  some 
  future 
  occasion. 
  At 
  present 
  I 
  will 
  cite 
  

   one 
  more 
  striking'example 
  furnished 
  by 
  the 
  salts 
  of 
  iron. 
  This 
  metal, 
  as 
  is 
  well 
  

   known, 
  furnishes 
  two 
  classes 
  of 
  salts, 
  in 
  one 
  of 
  which 
  the 
  molecule 
  is 
  bivalent, 
  

   the 
  atomic 
  number 
  being 
  .50, 
  in 
  the 
  other 
  class 
  the 
  molecule 
  becomes 
  quadriva- 
  

   lent, 
  with 
  a 
  combining 
  number 
  of 
  112. 
  Of 
  the 
  former 
  class 
  of 
  salts, 
  30 
  or 
  40 
  

   grains 
  can 
  be 
  introduced 
  into 
  the 
  veins 
  (in 
  dogs) 
  without 
  destroying 
  life, 
  whilst 
  

   3 
  or 
  4 
  grains 
  of 
  the 
  quadrivalent 
  compounds 
  are 
  fiital. 
  The 
  extremely 
  poison- 
  

   ous 
  effects 
  of 
  the 
  metals 
  of 
  the 
  platinum 
  group 
  with 
  their 
  high 
  atomic 
  weight, 
  

   is 
  another 
  instance 
  of 
  the 
  connection 
  of 
  atomic 
  weight 
  with 
  physiological 
  action. 
  

   The 
  above 
  observations 
  tend 
  to 
  confirm 
  an 
  opinion 
  I 
  expressed 
  in 
  a 
  paper 
  read 
  

   at 
  the 
  meeting 
  of 
  the 
  British 
  Association 
  for 
  the 
  Advancement 
  of 
  Science, 
  in 
  

   1845, 
  when 
  I 
  stated 
  : 
  " 
  In 
  considering 
  the 
  action 
  of 
  inorganic 
  compounds 
  on 
  

   living 
  beings, 
  it 
  is 
  clear 
  that 
  our 
  attention 
  must 
  not 
  be 
  directed 
  exclusively 
  to 
  

   the 
  chemical 
  properties 
  of 
  these 
  substances 
  ; 
  it 
  must 
  not 
  be 
  as 
  acids 
  or 
  alkalies 
  

   or 
  salts 
  that 
  their 
  action 
  on 
  living 
  beings 
  must 
  be 
  investigated, 
  but 
  as 
  regards 
  

   their 
  isomorphous 
  relations, 
  or 
  those 
  properties 
  which 
  are 
  evidently 
  connected 
  

   with 
  the 
  form 
  they 
  assume." 
  

  

  In 
  our 
  ordinary 
  chemical 
  reactions, 
  the 
  greater 
  the 
  atomic 
  weight 
  of 
  a 
  body 
  

   the 
  larger 
  the 
  quantity 
  that 
  must 
  be 
  used 
  to 
  form 
  the 
  diflerent 
  compounds 
  into 
  

   which 
  it 
  enters 
  ; 
  whilst 
  the 
  above 
  facts 
  show 
  that 
  with 
  certain 
  restrictions 
  the 
  

   very 
  reverse 
  of 
  this 
  is 
  the 
  case 
  in 
  the 
  reactions 
  it 
  produces 
  in 
  living 
  beings. 
  

   The 
  above 
  facts, 
  together 
  with 
  those 
  already 
  published, 
  justify 
  the 
  conclusion 
  

   tLat, 
  first 
  : 
  when 
  introduced 
  directly 
  into 
  the 
  blood, 
  each 
  member 
  of 
  an 
  isomor- 
  

   phous 
  group 
  gives 
  rise 
  to 
  analogous 
  reactions, 
  both 
  on 
  the 
  tissues 
  and 
  on 
  the 
  

   blood, 
  and 
  second 
  : 
  that 
  the 
  intensity 
  of 
  these 
  reactions 
  is 
  in 
  some 
  way 
  connected 
  

   with 
  the 
  relative 
  atomic 
  weight 
  of 
  the 
  substance 
  in 
  the 
  group 
  -to 
  which 
  it 
  be- 
  

   longs. 
  Exceptions 
  undoubtedly 
  present 
  themselves 
  to 
  the 
  above 
  generalizations, 
  

   nor 
  is 
  it 
  at 
  all 
  surprising 
  that 
  in 
  the 
  present 
  imperfect 
  state 
  of 
  our 
  knowledge 
  

   as 
  regards 
  atomic 
  physics, 
  that 
  such 
  should 
  be 
  the 
  case; 
  but 
  still, 
  the 
  number 
  of 
  

   instances 
  in 
  which 
  a 
  well 
  marked 
  connection 
  is 
  found 
  between 
  isomorphism, 
  

  

  