﻿I^ROCEEDINGS 
  OF 
  THE 
  FOURTH 
  EfJ^TOMOLOGlCAL 
  MEETING 
  165 
  

  

  to 
  a 
  fixed 
  quantity 
  of 
  water 
  (100 
  c. 
  c.) 
  ; 
  Graph 
  2, 
  representing 
  a 
  fixed 
  

   quantity 
  of 
  the 
  salt 
  (0-001 
  gm.) 
  in 
  a 
  constant 
  surface-area 
  of 
  water 
  (6 
  

   inches 
  diameter), 
  but 
  with 
  varying 
  depths 
  ; 
  and 
  Graph 
  3, 
  representing 
  

   a 
  fixed 
  quantity 
  of 
  the 
  salt 
  (0-001 
  gm.) 
  in 
  a 
  constant 
  depth 
  of 
  10 
  mm., 
  

   but 
  with 
  varying 
  surface-areas.* 
  

  

  We 
  might 
  assume 
  one 
  or 
  more 
  of 
  the 
  following 
  circumstances 
  under 
  

   which 
  death 
  might 
  occur 
  : 
  — 
  

  

  (i) 
  Presence 
  of 
  HgClg 
  in 
  the 
  calomel 
  as 
  impurity, 
  but 
  (1) 
  the 
  addi- 
  

   tion 
  of 
  KOH 
  to 
  a 
  saturated 
  solution 
  of 
  the 
  HgCl 
  did 
  not 
  give 
  

   the 
  yellow 
  precipitate, 
  the 
  characteristic 
  reaction 
  of 
  HgCL, 
  

   and 
  (2) 
  saturated 
  solution 
  of 
  the 
  calomel 
  failed 
  to 
  kill 
  the 
  

   larvaj. 
  

  

  (ii) 
  Gradual 
  conversion 
  of 
  HgCl 
  into 
  HgClg, 
  but 
  (1) 
  the 
  water 
  in 
  

   which 
  the 
  salt 
  had 
  been 
  allowed 
  to 
  stand 
  for 
  a 
  considerable 
  

   period 
  did 
  not 
  answer 
  the 
  KOH 
  test 
  for 
  HgCL 
  (2) 
  no 
  traces 
  

   of 
  the 
  liquid 
  metal 
  could 
  be 
  detected, 
  as 
  the 
  conversion 
  of 
  

   the 
  salt 
  into 
  HgClg 
  would 
  have 
  been 
  accompanied 
  by 
  a 
  

   separation 
  of 
  mercury, 
  and 
  (3) 
  0-001 
  per 
  cent. 
  HgCla 
  failed 
  

   to 
  kill 
  the 
  larvae 
  (Graph 
  4). 
  

  

  It 
  is 
  then 
  probably 
  the 
  solid 
  state 
  in 
  which 
  the 
  salt 
  acts. 
  HgCl, 
  

   even 
  in 
  the 
  solid 
  condition, 
  is 
  said 
  to 
  be 
  capable 
  of 
  acting 
  cutaneously 
  

   on 
  the 
  human 
  body, 
  the 
  action 
  being 
  hastened 
  with 
  the 
  stimulation 
  

   of 
  diaphoresis.! 
  It 
  is 
  not 
  improbable 
  that 
  this 
  might 
  also 
  be 
  the 
  case 
  

   with 
  mosquito 
  larvae. 
  On 
  the 
  other 
  hand 
  the 
  fact 
  that 
  the 
  pupae 
  had 
  

   been, 
  in 
  most 
  cases, 
  found 
  to 
  escape 
  unhurt, 
  lends 
  weight 
  to 
  the 
  assump- 
  

   tion 
  that 
  the 
  salt 
  acts 
  orally. 
  

  

  An 
  interesting 
  feature 
  of 
  the 
  results 
  is 
  the 
  exceedingly 
  small 
  quantity 
  

   of 
  the 
  salt 
  (0-001 
  per 
  cent.) 
  necessary 
  to 
  kill 
  the 
  larvae 
  ; 
  but 
  the 
  maximum 
  

   therapeutic 
  dose 
  of 
  HgCl 
  for 
  man 
  being 
  5 
  grains 
  onlyj, 
  a 
  mere 
  trace 
  of 
  

   the 
  salt 
  should 
  be 
  sufficient 
  to 
  kill 
  a 
  mosquito 
  larva. 
  On 
  the 
  other 
  

   hand 
  the 
  maximum 
  therapeutic 
  dose 
  of 
  HgClg 
  being 
  ^ 
  grainj, 
  failure 
  of 
  

   0-001 
  per 
  ceni!. 
  HgCla 
  to 
  affect 
  the 
  larvee 
  might 
  seem 
  inexplicable, 
  especi- 
  

   ally 
  in 
  the 
  face 
  of 
  the 
  fact 
  that 
  0-001 
  per 
  cent. 
  HgCl, 
  killed 
  them 
  ; 
  but 
  this 
  

   can 
  be 
  explained 
  away 
  by 
  the 
  fact 
  that 
  the 
  attribution 
  of 
  " 
  percentage 
  " 
  

   to 
  HgCl 
  in 
  relation 
  to 
  quantity 
  of 
  water 
  is 
  meaningless, 
  the 
  solubihty 
  

   of 
  the 
  salt 
  being 
  practically 
  negligible. 
  

  

  * 
  The 
  results 
  of 
  all 
  the 
  experiments 
  done 
  are 
  not 
  shown 
  in 
  the 
  graphs 
  : 
  only 
  a 
  few 
  

   typical 
  sets 
  are 
  represented; 
  and 
  in 
  order 
  to 
  emphasize 
  the 
  behaviour 
  of 
  individual 
  

   larvae, 
  the 
  customary 
  method 
  of 
  representing 
  the 
  average 
  result 
  has 
  not 
  been 
  adopted. 
  

  

  t 
  Materia 
  Medica 
  and 
  Therapeutics 
  (Bruce). 
  

  

  t 
  Ibid. 
  

  

  