HAROLD C. ERNST 



cause of cancer, the ripening of butter, and the fermenta- 

 tion of wines by special cultures, are all matters of common 

 occurrence illustrative of what I mean. 



A review of the ways in which it has been sought to se- 

 cure a specific treatment for the infectious diseases may, 

 however, prove interesting and instructive, and may serve to 

 show how disastrous it would be to depend upon present 

 book knowledge. The inference to be drawn is, apparently, 

 that each process is a problem by itself, and must be worked 

 out for itself, by the combined efforts of every one compe- 

 tent to do so. 



First, there is vaccination against smallpox ; this is really 

 the substituting of a mild type of disease (cow-pox) for a 

 malignant form of a similar but different disease, without 

 reference being had to the actual causative agent in either. 



Then came the efforts of Pasteur to secure protection 

 against anthrax, based upon the fact shown in the labora- 

 tory, that cultures of the bacillus of this disease could be 

 attenuated 'in virulence, upon being subjected to certain ab- 

 normal conditions ; and that when thus attenuated they 

 merely made the animal sick, but did not kill after being 

 inoculated : when the animal had recovered, it was found 

 to be in a condition to resist the action of cultures in full 

 virulence. In other words, here was a method of protec- 

 tion against a malignant form of disease by subjecting the 

 patient to an attack of a mild form of the same disease (not 

 a different disease, as seen in vaccination]. This successful 

 production of immunity by an attenuated virus led to many 

 efforts in the same direction, without great success thus far 

 in diseases attacking man, except in rabies. And here the 

 result is somewhat different, for we do not in this case deal 

 with the actual specific cause alone, but with an emulsion 

 of the tissue in which this cause is known to be present. 



Then came tuberculin and mallein, both dealing with 

 the intracellular products of growth of the specific causes 



