126 
FRANK S. BILLINGS. 
ner, from every outbreak of “ hog cholera” which I have visited 
in Nebraska during the summer, fall and winter of 1886. The 
first hog I examined was upon July 8, and I was fortunate enough 
to have a pure cultivation of one bacterium in every tube inocu¬ 
lated. 
The field examinations and experiments will be reported in a 
future paper. 
This organism is very minute, and requires at least 1-18 oil 
immersion, aided by the Abbe condensor in order to study its pe- 
culiarites successfully. My own work has been with an instru¬ 
ment made expressly by E. Leitz, of Wetzlar, Germany, which, 
while not costing as much, was proved by the most exacting tests 
to be equal to the best Zeiss; it is provided with a one-twelfth, 
one-eighteenth, one-twentieth oil immersion, the latter of which I 
have used in these studies. 
For a long time 1 have been of the opinion that we are not 
exact enough in the differential choice of our language when 
speaking of phenomena of micro-organismal life, especially with 
regard to the differentiation between morphological and biological 
phenomena. 
Morphological phenomena have reference to shape , size, out¬ 
line , alone. 
Biological to everything else connected with these organisms. 
The mistake is too often made of speaking of the appearances 
of the micro-organisms, when colored, as morphological appear¬ 
ances, whereas they are unquestionably of a biological, chemical 
character ; dependent upon the chemical affinities of certain parts 
of the protoplasm for the different coloring materials. While 
unquestionably, as in the case of the micro-organisms of the 
American and German swine plague, the “ wildseuche” of Ger¬ 
many, rabbit and mouse septicaemia, and those of some other dis¬ 
eases, this coloring reaction of the germ differentiates its proto¬ 
plasm into two distinctly separate materials chemically, and this 
differentiation manifests itself, to the eye of the observer, in a 
certain morphological sense; still the phenomena are of a biolog¬ 
ical and not morphological nature. 
Again, the artificial cultivations of micro-organism in or upon 
