

MY WORK AND BACTERIOLOGY 313 
Hitherto they have shown not the least disposi- 
tion to modify their methods, with a view to seek 
such results as I have obtained. The modification 
needed would be, of course, to heat their nourishing 
fluids (semi-solid media would not be favourable for 
the trial) only sufficiently to destroy pre-existing 
living things, and then to take suitable means, by 
the agency of heat or light, to favour the possible 
engendering of new living matter. 
Their exclusive occupation with their own 
methods is unfortunate simply because it has 
so long had the effect of giving sanction to ultra- 
contagionist doctrines. But, as | have pointed out, 
the prosecution of their own researches, by their 
own methods, is now tending rapidly to show that 
wider views are necessary, and that they must 
recognise as facts what for so long it has been their 
habit to deny—namely, that contagious and infec- 
tious diseases frequently arise de novo. 
Still this view is being forced upon them inde- 
pendently of any necessary belief in the ‘‘ spontaneous 
generation” of micro-organisms. It comes, as I 
have pointed out, as a consequence of multitudinous 
observations tending to show that pathogenic are 
constantly being derived, as Lehmann and Neumann 
say, from non-pathogenic organisms—by reason of 
gradual alterations brought about not so much in 
their form as in the metabolic processes inseparable 
from their life and growth. 
When a contagious disease is once established, of 
course everything must be done, as far as possible, 
to check its course in the individual; and likewise 
