﻿550 
  Seventh 
  Anmal 
  ]\p:roRT 
  ok 
  the 
  

  

  ably 
  ca\ised 
  by 
  a 
  certain 
  dose 
  it 
  is 
  impossible 
  to 
  render 
  the 
  system 
  

   immune 
  to 
  the 
  bacilli 
  of 
  tuberculosis 
  by 
  hypodermatic 
  injections 
  of 
  

   tL-e 
  unchanged 
  bacilli. 
  

  

  Ilis 
  subsequent 
  efforts 
  were 
  directed 
  toward 
  the 
  discovery 
  of 
  a 
  

   method 
  of 
  breaking 
  up 
  the 
  bacilli 
  by 
  mechanical 
  means 
  in 
  order 
  

   to 
  facilitate 
  their 
  absorption. 
  He 
  had 
  discovered 
  in 
  previous 
  ex- 
  

   periments 
  that 
  the 
  bacteria 
  of 
  phthisis 
  consists 
  of 
  two 
  peculiar 
  

   chemical 
  components 
  which 
  belong 
  in 
  the 
  category 
  of 
  under-satu- 
  

   irated 
  fatty 
  acids. 
  One 
  of 
  these 
  acids 
  is 
  soluble 
  in 
  dilute 
  alcohol, 
  

   and 
  is 
  easily 
  turaed 
  to 
  soap 
  by 
  contact 
  with 
  natron 
  lye; 
  the 
  other 
  

   is 
  only 
  soluble 
  in 
  pure 
  boiling 
  alcohol 
  or 
  ether, 
  and 
  is 
  very 
  diffi- 
  

   cult 
  to 
  convert 
  into 
  soap. 
  These 
  fatty 
  acids 
  are 
  shovm 
  by 
  micro- 
  

   scopical 
  examination 
  to 
  form 
  a 
  cohesive 
  and 
  protective 
  layer 
  

   around 
  the 
  bacillus, 
  which 
  prevents 
  its 
  absorption. 
  For 
  some 
  

   time 
  the 
  various 
  attempts 
  to 
  destroy 
  this 
  protective 
  coating 
  failed 
  

   utterly. 
  It 
  was 
  only 
  when 
  the 
  cultures 
  were 
  well 
  dried 
  and 
  

   beaten 
  in 
  a 
  mortar 
  for 
  some 
  time 
  that 
  the 
  number 
  of 
  bacilli 
  com- 
  

   menced 
  to 
  decrease. 
  To 
  get 
  rid 
  of 
  those 
  that 
  remained 
  Koch 
  

   placed 
  the 
  substance 
  that 
  had 
  been 
  beaten 
  in 
  the 
  mortar 
  in 
  dis- 
  

   tilled 
  water 
  and 
  subjected 
  it 
  to 
  the 
  action 
  of 
  a 
  powerful 
  centri- 
  

   fugal 
  separator. 
  The 
  products 
  obtained 
  by 
  this 
  process 
  were 
  a 
  

   white, 
  opalescent, 
  and 
  completely 
  transparent 
  fluid, 
  which 
  con- 
  

   tains 
  no 
  bacilli, 
  and 
  a 
  slimy, 
  viscous 
  sediment. 
  This 
  sediment 
  is 
  

   subjected 
  to 
  the 
  same 
  treatment 
  as 
  the 
  bacilli, 
  and 
  the 
  above-de- 
  

   scribed 
  process 
  is 
  repeated 
  until 
  the 
  entire 
  sediment 
  is 
  dissolved 
  

   into 
  a 
  series 
  of 
  clear 
  fluids. 
  Koch 
  experimented 
  with 
  the 
  fluids 
  

   obtained, 
  first 
  upon 
  animals 
  and 
  then 
  upon 
  human 
  beings, 
  and 
  

   found 
  that 
  the 
  first 
  fluid 
  possessed 
  different 
  qualities 
  from 
  the 
  

   fluids 
  that 
  had 
  been 
  obtained 
  by 
  a 
  repetition 
  of 
  the 
  treatment 
  in 
  

   the 
  centrifugal 
  separator, 
  all 
  of 
  which 
  possessed 
  identical 
  quali- 
  

   ties. 
  

  

  The 
  fluid 
  that 
  had 
  been 
  subjected 
  to 
  the 
  centrifugal 
  separator 
  

   once 
  is 
  designated 
  tuberculin 
  O 
  or 
  TO. 
  The 
  different 
  fluids 
  ob- 
  

   tained 
  by 
  repetitions 
  of 
  the 
  original 
  process 
  are 
  designated 
  as 
  

   tuberculin 
  R 
  or 
  TE. 
  

  

  