﻿Commissioner 
  of 
  Agriculture. 
  531 
  

  

  cal 
  profession, 
  there 
  are 
  still 
  those 
  who 
  doubt 
  the 
  experimentally 
  

   tested 
  and 
  practically 
  demonstrated 
  possibilities 
  of 
  this 
  substance. 
  

   Of 
  the 
  bacterial 
  products 
  which 
  in 
  recent 
  years 
  have 
  come 
  into 
  

   prominence, 
  few, 
  if 
  any, 
  occupy 
  a 
  place, 
  either 
  in 
  human 
  or 
  com- 
  

   parative 
  medicine, 
  where 
  an 
  accurate 
  and 
  wide-spread 
  knowledge 
  

   of 
  the 
  conditions 
  Hmiting 
  their 
  elfectiveness 
  is 
  more 
  urgently 
  de- 
  

   manded 
  than 
  for 
  tuberculin. 
  The 
  important 
  position 
  it 
  holds 
  

   in 
  sanitary 
  medicine 
  and 
  the 
  powerful 
  agent 
  it 
  may 
  become 
  in 
  

   the 
  hands 
  of 
  those 
  who 
  have 
  to 
  do 
  with 
  bovine 
  tuberculosis 
  em- 
  

   phasize 
  the 
  necessity 
  of 
  such 
  a 
  knowledge. 
  

  

  Within 
  the 
  limits 
  of 
  this 
  paper 
  it 
  will 
  be 
  impossible 
  to 
  discuss 
  

   in 
  detail 
  the 
  numerous 
  questions 
  which 
  naturally 
  suggest 
  them- 
  

   selves 
  in 
  the 
  effort 
  to 
  give 
  an 
  account 
  of 
  the 
  present 
  knowledge 
  of 
  

   tuberculin, 
  as 
  to 
  what 
  it 
  is 
  and 
  what 
  it 
  will 
  do. 
  I 
  propose, 
  how- 
  

   ever, 
  to 
  treat 
  somewhat 
  fully 
  of 
  the 
  more 
  essential 
  features 
  in 
  its 
  

   preparation 
  and 
  in 
  its 
  usej 
  which, 
  if 
  thoroughly 
  understood, 
  seem 
  

   sufficient 
  to 
  answer 
  many 
  of 
  the 
  objections 
  to 
  its 
  employment 
  as 
  

   an 
  aid 
  in 
  detecting 
  tuberculosis 
  in 
  cattle. 
  Much 
  of 
  the 
  honest 
  

   opposition 
  to 
  its 
  use, 
  in 
  this 
  State 
  at 
  least, 
  seems 
  to 
  come 
  from 
  a 
  

   lack 
  of 
  definite 
  knowledge 
  of 
  its 
  true 
  nature 
  and 
  powers. 
  

  

  At 
  the 
  outset 
  it 
  is 
  important 
  to 
  note 
  that 
  we 
  are 
  dealing 
  with 
  a 
  

   problem 
  in 
  which 
  the 
  chief 
  factors 
  are 
  immeasured, 
  and, 
  to 
  a 
  cer- 
  

   tain 
  degree, 
  unmeasurable 
  vital 
  forces. 
  In 
  the 
  very 
  beginning 
  

   we 
  are 
  confronted 
  with 
  the 
  manifestations 
  of 
  life 
  itself. 
  The 
  

   problem 
  is 
  one 
  in 
  biology, 
  where 
  unexpected 
  deviations 
  may 
  occur 
  

   as 
  a 
  natural, 
  though 
  unexplained, 
  result 
  of 
  the 
  immediate 
  condi- 
  

   tions 
  of 
  life. 
  If 
  this 
  fundamental 
  principle 
  is 
  taken 
  into 
  account 
  

   it 
  will 
  teach 
  us 
  that 
  many 
  of 
  the 
  objections 
  to 
  tuberculin 
  which 
  

   have 
  been 
  held 
  up 
  as 
  insurmountable 
  because 
  they 
  were 
  not 
  im- 
  

   mediately 
  explained 
  to 
  the 
  satisfaction 
  of 
  the 
  objector, 
  cannot, 
  

   from 
  the 
  very 
  nature 
  of 
  things, 
  be 
  explained 
  until 
  we 
  have 
  more 
  

   knowledge 
  of 
  the 
  mysterious 
  processes 
  of 
  life 
  and 
  disease. 
  

  

  Tuberculin, 
  as 
  we 
  know 
  it 
  to-day, 
  is 
  the 
  concentrated 
  liquid, 
  

   usually 
  glycerinated 
  bouillon, 
  on 
  which 
  tubercle 
  bacilli 
  have 
  

  

  