APPENDIX 



ON THE GREAT IMPORTANCE FROM THE POINT OF VIEW OF 

 MEDICAL SCIENCE OF THE PROOF THAT BACTERIA AND 

 THEIR ALLIES ARE CAPABLE OF ARISING DE NOVO' 



THE intimate relations that have been proved to exist between 

 microorganisms and so many of the contagious or com- 

 municable diseases, and the discovery that in many cases the 

 organisms in question act as the veritable contagia by means of 

 which such diseases are spread from person to person, have 

 exercised such an enormous influence over the minds of medical 

 men that they have led to the almost universal establishment of 

 ultra-contagionist views in rpgard to all these diseases. Just, it is 

 thought, as organisms are propagated only, and do not arise de novo, 

 so the reigning doctrine in medicine has been for some time, and 

 still is, that contagious diseases are propagated only and never 

 arise de novo. The breaking down of the prejudice in regard to 

 organisms, by showing that they can originate independently of 

 pre-existing microorganisms of like kind would of necessity exert 

 a powerful influence over medical doctrines, and would pave the 

 way for the admission that contagious diseases may also arise de 

 novo instead of being only disseminated by contagion. Short of a 

 proof of this kind there seems less chance of any such widening of 

 doctrine being brought about. 



To show the kind of feeling that exists I may recall the fact that 

 one of the most distinguished physicians in this country not very 

 long since said : = " If I can trace contagion in a very large number 

 of the so-called specific diseases I consider it more reasonable to 

 assume contagion in the minority than look about for another 

 cause." And he went on to say that, as many of these diseases 



' This article first appeared in the columns of " The Lancet," for October 31, 

 1903 ; but the bearing of my views on medical science has been so much mis- 

 represented, that I have thought it well to reproduce it here. 



' Letter from Sir Samuel Wilks, " British Medical Journal," December 23, 1893. 



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