﻿534 
  Sevemh 
  Annual 
  Eepokt 
  of 
  the 
  

  

  method 
  of 
  diluting 
  the 
  tuberculin 
  in 
  the 
  laboratory 
  before 
  send- 
  

   ing 
  it 
  out. 
  This 
  has 
  teen 
  the 
  practice 
  of 
  the 
  Bureau 
  of 
  Animal 
  

   Industry^ 
  for 
  a 
  number 
  of 
  years. 
  Equally 
  good 
  results 
  are 
  

   obtained 
  by 
  concentrating 
  the 
  saturated 
  culture 
  to 
  the 
  point 
  

   where 
  2 
  c.c. 
  contains 
  an 
  equivalent 
  of 
  the 
  0.25 
  c.c. 
  of 
  the 
  highly 
  

   concentrated 
  lymph. 
  This 
  process 
  avoids 
  the 
  necessity 
  of 
  dilu- 
  

   tions, 
  and 
  M'ith 
  tlic 
  additions 
  of 
  a 
  few 
  drops 
  of 
  carbolic 
  acid 
  the 
  

   weaker 
  solution 
  keeps 
  perfectly. 
  

  

  The 
  questions 
  which 
  perplexed 
  us 
  a 
  few 
  years 
  ago 
  concerning 
  

   the 
  virulence 
  of 
  the 
  tubercle 
  bacilli 
  to 
  be 
  used 
  in 
  making 
  an 
  

   efficient 
  tuberculin 
  have 
  for 
  the 
  greater 
  part 
  been 
  answered. 
  

   Trudeau, 
  Baldwin, 
  and 
  de 
  Schweinitz 
  have 
  experimented 
  in 
  this 
  

   line, 
  and 
  have 
  published 
  to 
  the 
  effect 
  that 
  attenuated, 
  non-viru- 
  

   lent 
  tubercle 
  bacilli 
  will 
  produce 
  quite 
  as 
  strong 
  a 
  tuberculin 
  as 
  

   the 
  more 
  virulent 
  forms. 
  Thus, 
  Trudeau 
  and 
  BaldAvin*' 
  obtained 
  

   from 
  non-virulent 
  tubercle 
  bacilli 
  tuberculin 
  of 
  such 
  strength 
  

   that 
  0.10 
  c.c. 
  usually 
  killed 
  six 
  weeks' 
  tuberculous 
  guinea-pigs. 
  

   In 
  a 
  more 
  recent 
  article 
  Trudeau^ 
  makes 
  this 
  important 
  state- 
  

   ment 
  : 
  " 
  My 
  own 
  observations 
  so 
  far 
  have 
  tended 
  to 
  the 
  belief 
  

   that 
  as 
  efficient 
  a 
  tuberculin 
  can 
  be 
  made 
  from 
  attenuated 
  as 
  from 
  

   virulent 
  cultures; 
  but 
  as 
  the 
  non-vindent 
  cultures 
  grow 
  generally 
  

   more 
  luxuriantly, 
  it 
  may 
  be 
  that 
  they 
  produce 
  more 
  toxin, 
  

   though 
  of 
  less 
  potency, 
  while 
  the 
  virulent 
  germs 
  elaborate 
  a 
  more 
  

   toxic 
  product, 
  but 
  less 
  in 
  quantity." 
  E. 
  A. 
  de 
  Schweinitz^ 
  states 
  

   that 
  " 
  attenuated 
  tubercle 
  bacilli^ 
  did 
  not 
  lose 
  the 
  property 
  of 
  pro- 
  

   ducing 
  or 
  secreting 
  the 
  active 
  principle 
  of 
  tuberculin." 
  

  

  Concerning 
  the 
  source 
  of 
  the 
  bacilli 
  used 
  in 
  making 
  tuberculin, 
  

   it 
  seems 
  that 
  cultures 
  of 
  the 
  human, 
  or 
  sputum, 
  bacillus 
  are 
  ordi- 
  

  

  B 
  E. 
  A. 
  de 
  Schweinitz 
  (Year-book 
  of 
  the 
  United 
  States 
  Department 
  of 
  Agri- 
  

   culture 
  for 
  1898, 
  p. 
  111). 
  He 
  gives 
  in 
  this 
  article 
  a 
  detailed 
  account 
  of 
  the 
  

   method 
  of 
  preparing 
  tuberculin 
  and 
  the 
  results 
  obtained 
  from 
  the 
  thousands 
  

   of 
  doses 
  which 
  have 
  been 
  distributed 
  by 
  the 
  Bureau. 
  

  

  6 
  American 
  Journal 
  of 
  the 
  Medical 
  Sciences. 
  December, 
  1898^ 
  January, 
  1899. 
  

  

  7 
  Johns 
  Hopkins 
  Hospital 
  Bulletin, 
  1899, 
  vol. 
  x, 
  p. 
  121. 
  

  

  8 
  Loc. 
  cit. 
  

  

  8 
  These 
  bacilli 
  were 
  attenuated 
  in 
  1893 
  (original 
  description 
  in 
  Medical 
  

   News, 
  December 
  8, 
  1894), 
  and 
  have 
  been 
  used 
  since 
  that 
  time, 
  he 
  states, 
  "with 
  

   great 
  advantage 
  both 
  in 
  preparing 
  tuberculin 
  and 
  in 
  immunizing 
  animals 
  

   against 
  virulent 
  tubercle 
  bacilli." 
  

  

  