BY JOHN THOMSON, M.B. 83 
how truly, that—given the choicest soil for some special 
crop—not a blade would grow, if all the factors—the earth, 
seed, water and air—had been absolutely deprived of bacterial 
life. 
Certainly it has been proved that the complex process 
of nitrification, the process by which nitrogen from organic 
substances—decomposing animal and_ vegetable bodies, 
manures, etc.—is transformed or mineralised into ammonia, 
nitrous and nitric acids depends upon micro-organic life, 
and that the conversion is a double one. One set of bacteria 
changes the ammonia into nitrous acid, and a totally different 
set transforms’ the latter into nitric, which unites with soil 
ingredients to form nitrates. The process is an oxydising 
one, but it is a fundamental of agricultural chemistry. 
As baking (panary fermentation) and brewing (vinous 
fermentation) are both dependent upon the behaviour of the 
yeast plant—of which, by-the-way, there are many varieties— 
and as yeasts are half brothers of the bacteria, one may truly 
assert that our lunch, of bread, butter, cheese, and beer, 
with salad and its vinegar dressing and the subsequent 
soothing weed, is composed of articles, whose very existence 
is undoubtedly dependent upon or absolutely due to micro- 
organic life; and, judging from the number of bacteria found 
in the mouth, and also from the number on the mucous 
surface of the prima via, it is at least probable, that the process 
of digestion is more or less dependent upon bacterial aid. 
And another, a more recent, and, if successful, perhaps 
the most important, of all the friendly aids which man receives 
from lowly hfe is the bacterial treatment of sewage, or as it 
has been referred to as “‘ simply allowing Nature to fulfil her 
function by means of bacteria.” 
The Pathogenic Organisms will now claim our attention, 
and as these are responsible for the Infective Diseases. Kan- 
thack’s classification of the latter, as 1t appears in the first 
volume of Clifford Allbutt’s System of Medicine, may be 
accepted as authoritative. And although this was published 
in 1896, the years since then have made but little change. 
The lst gives 17 diseases of more or less established 
bacteriology :—19 are catalogued as uncertain ; 5 appear as 
