FIXITY OF BACTERIAL SPECIES 25 



logists, Koch, in particular supported the doctrine. For twenty- 

 years or so he laid down that the tubercle bacillus which he had 

 discovered was identical in its properties from whatever animal 

 it was isolated, whether from man, the ox, or bird, opposing 

 Straus and others when they called attention to the marked 

 distinction in the properties of the human and avian types. 

 You will remember how suddenly and dramatically he turned 

 round at the great Tuberculosis Congress in London, announc- 

 ing that the human and bovine forms of bacillus were absolutely 

 distinct species — incidentally without any acknowledgment of 

 the work done by American workers, Theobald Smith, Dinwiddie 

 and Frothingham, in establishing these differences between the 

 two types, and incidentally, also, he being a Government servant, 

 to the apparent material advantage of the agrarian party in 

 Germany. Many of my readers will recall the consternation 

 of the hygienists and of the various governmental Agricultural 

 Departments when he pointed out that, being distinct species, 

 there was little or no danger of the disease being conveyed from 

 cattle to man by the milk. It has cost Great Britain alone 

 thousands of pounds and years of work of a Royal Commission 

 to demonstrate Koch's error, and show that notwithstanding 

 recognizable and characteristic differences between the typus 

 humanus and typus bovinus, nevertheless intermediate forms 

 exist, and that the typus bovinus can obtain a lodgment and 

 develop lesions, more particularly in susceptible children during 

 the milk-drinking period. Koch would never have perpetrated 

 his successive blunders but for his firm conviction that environ- 

 ment is incapable of altering the properties of bacteria. 



Koch's attitude in this matter has affected me from the 

 fact that from the time of my thesis for the M.D. at Cambridge 

 I have taught the variability of the bacteria, 1 as again from 

 the fact that in 1899, many months before Koch's notorious 

 pronouncement, I had, in an address delivered to the Canadian 

 Medical Association at Toronto, 2 brought together all the data 

 bearing upon the difference between human and bovine tuber- 

 culosis and their causative agents, and at a request which reached 



1 Vide the article upon the "Variability of the Bacteria" reprinted as 

 Chapter I. of Part II. of this volume. 



2 On the significance of Bovine Tuberculosis and its eradication and pre- 

 vention in Canada (read before the Canadian Medical Association, Toronto, 

 August 30, 1899), Philadelphia Medical Journal, December 30, 1899. 



