﻿Commissioner 
  of 
  Agriculture. 
  533 
  

  

  new 
  gro^^'th 
  begins; 
  but 
  if 
  a 
  young, 
  growing 
  culture 
  is 
  used, 
  it 
  

   begins 
  at 
  once, 
  or, 
  better, 
  continues 
  with 
  but 
  slight 
  interruption, 
  

   as 
  in 
  the 
  mother 
  flask. 
  However, 
  unfavorable 
  conditions 
  of 
  

   medium 
  or 
  temperature 
  may 
  retard 
  these 
  growths. 
  It 
  is 
  usually 
  

   the 
  delay 
  in 
  getting 
  the 
  tubercle 
  bacilli 
  to 
  begin 
  to 
  multiply 
  in 
  the 
  

   newly 
  inoculated 
  medium 
  that 
  causes 
  the 
  variation 
  in 
  the 
  length 
  

   •of 
  time 
  necessary 
  to 
  incubate 
  the 
  cultures 
  before 
  they 
  contain 
  the 
  

   proper 
  amount 
  of 
  the 
  tuberculin 
  elements.^ 
  

  

  If 
  the 
  method 
  of 
  preparation 
  is 
  further 
  examined 
  it 
  will 
  be 
  

   seen 
  that 
  tuberculin 
  cannot 
  possibly 
  contain 
  living 
  tubercle 
  bacilli. 
  

   It 
  is 
  heated, 
  on 
  two 
  occasions, 
  to 
  a 
  temperature 
  and 
  for 
  a 
  length 
  

   of 
  time 
  far 
  in 
  excess 
  of 
  that 
  required 
  to 
  destroy 
  the 
  bacilli, 
  be- 
  

   sides 
  being 
  passed 
  through 
  a 
  filter 
  capable 
  of 
  removing 
  all 
  

   bacteria. 
  It 
  is 
  a 
  physical 
  impossibility, 
  therefore, 
  for 
  tuberculin 
  

   which 
  has 
  been 
  properly 
  made 
  to 
  cause 
  tuberculosis. 
  Whatever 
  

   physiological 
  disturbances 
  it 
  may 
  excite, 
  it 
  cannot 
  impart 
  that 
  

   which 
  it 
  does 
  not 
  possess, 
  namely, 
  the 
  contagiuin 
  vivum 
  of 
  the 
  

   disease. 
  

  

  The 
  original 
  tuberculin 
  or 
  lymph 
  of 
  Koch 
  was 
  concentrated 
  to 
  

   one-tenth 
  of 
  the 
  volume 
  of 
  the 
  saturated 
  cultures. 
  This 
  gave 
  a 
  

   thick, 
  syrupy 
  liquid, 
  owing 
  to 
  the 
  presence 
  of 
  the 
  glycerine. 
  The 
  

   diagnostic 
  dose 
  which 
  came 
  to 
  be 
  recommended 
  for 
  cattle 
  of 
  

   medium 
  weight 
  was 
  0.25 
  c.c.^ 
  On 
  account 
  of 
  its 
  consistency 
  as 
  

   well 
  as 
  the 
  minuteness 
  of 
  the 
  dose 
  it 
  was 
  found 
  to 
  be 
  practicable 
  

   to 
  dilute 
  this 
  quantity 
  with 
  seven 
  parts 
  of 
  a 
  diluent. 
  A 
  weak 
  

   solution 
  of 
  carbolic 
  acid 
  was 
  ordinarily 
  used. 
  The 
  difficulties 
  and 
  

   dangers 
  involved 
  in 
  making 
  the 
  dilutions 
  in 
  the 
  field* 
  led 
  to 
  the 
  

  

  2 
  The 
  occasional 
  reports 
  of 
  poor 
  tuberculin 
  may 
  be 
  explained 
  in 
  this 
  way: 
  

   Early 
  in 
  my 
  experience 
  with 
  tuberculin, 
  a 
  quantity 
  was 
  made 
  from 
  vigorous 
  

   cultures 
  that 
  had 
  been 
  incubated 
  for 
  the 
  full 
  time. 
  When 
  it 
  was 
  tested 
  it 
  failed 
  

   to 
  give 
  a 
  reaction. 
  Upon 
  seeking 
  an 
  explanation, 
  the 
  notes 
  showed 
  that 
  the 
  

   growth 
  in 
  the 
  flasks 
  taken 
  was 
  retarded 
  for 
  three 
  weeks 
  and 
  very 
  feeble 
  for 
  

   two 
  more. 
  Subsequently 
  an 
  excellent 
  tuberculin 
  was 
  made 
  from 
  the 
  same 
  

   original 
  culture. 
  

  

  3 
  Dr. 
  Kinncll 
  of 
  Pittsfield, 
  Mass., 
  has 
  reported 
  equally 
  good 
  reactions 
  

   with 
  two- 
  thirds 
  of 
  a 
  minim. 
  (Journal 
  of 
  Comparative 
  Pathology 
  and 
  Thera- 
  

   peutics, 
  1894, 
  vol. 
  vii, 
  p. 
  182.) 
  

  

  4 
  Dr. 
  Cooper 
  Curtice 
  gave 
  detailed 
  directions 
  for 
  making 
  the 
  dilutions 
  in 
  the 
  

   field, 
  as 
  well 
  as 
  for 
  the 
  test 
  generally, 
  in 
  the 
  Annual 
  Report 
  of 
  the 
  Bureau 
  of 
  

   Animal 
  Industry 
  for 
  1895-1896, 
  p. 
  283. 
  

  

  