1889.1 Bacteriology. 169 
ing organism will be found capable of gelatinising the casein 
of milk." 
As regards the reduction of nitrates, Warington states 
that out of twenty-five organisms seven were entirely with- 
out reducing power, one produced a mere trace of nitrite, and 
one only a very small quantity : the remaining sixteen re- 
duced nitrates in broth, with considerable vigor. With the 
possible exception of one culture, the reduction to nitrites 
would appear to have occurred without the production of ni- 
trogen, oxides of nitrogen, or ammonia. 
The many investigations of the past few years on the rela- 
tion of micro-organisms to the process of nitrification have 
met with little success so far as regards the isolation of a 
specific bacterium of nitrification. Warington's researches in 
this direction seem to have been little more fruitful than those 
of his predecessors. His experiments gave mostly negative 
results, and he concludes his paper with the observation : " An 
organism which nitrifies as soil nitrifies, has yet to be \^o- 
\2itQdr—{E.O. Jordan.) 
Bacteria, Microbes, or Micro-organisms .?— These 
terms are being used by various writers sometimes with pre- 
cision but more often as synonyms. Etymologically "mi- 
crobe " and "micro-organism" are equivalent terms, mean- 
ing simply " a little living thing." But " bacterium " meaning 
"a staff" is certainly not equivalent to the other two. An 
arrangement, perhaps as natural and simple as any, is to re- 
serve the term micro-organisms for all forms of life which are 
so small that it is impracticable to study them to any great 
extent with the naked eye. " Micro-organisms" would then 
be a usefully indefinite term including many animals as well 
as plants, e.g. the protozoa, rotifers, many Crustacea, indeed 
representatives of nearly every great group of invertebrates, 
diatoms, desmids, and other micro-algae, besides moulds, 
yeasts, bacteria, and other micro-fungi. The micro-organ- 
isms are only a general and very comprehensive group, divisi- 
ble, for convenience, into two lesser groups. 
These are, i , the Microscopical and 2, the Bacterial micro- 
organisms. 
The Bacterial micro-organisins are those which are too 
small to be successfully studied individually and are best 
investigated in masses by special " cultures." They mclude 
the bacteria together with, perhaps, the yeasts and certain 
moulds 
The Microscopical micro-organisms are those which can be 
successfully studied bv the microscope, individually, and with- 
out special "cultures'." They include all animal micro-or- 
