1901] MICROSCOPICAL JOURNAL. 51 
micro-organisms are most susceptible to the environ ment. 
Their life cycle is so short that they are able to adapt 
themselves to changing conditions much more readily than 
is possible in the animal cells. What is true of one germ, 
may or may not be true of another; each has its own range 
of temperature, food conditions and environment in which 
it becomes pathogenic or harmless. The effects of envi- 
ronment may be demonstrated by placing germs under 
different conditions and noting the results. 
Most students are familiar with the results of growing 
the Leeffler bacilli on agar agar and other media. The ba- 
cilli of anthrax vary greatly under different conditions. 
Prof. Adami has shown how the bacillus colli changes 
from the bacillus form to the coccus, as it passes through 
the tissues. Because of these morphological changes, it 
is difficult to identify germs by form alone. While they 
may resemble each other in form, they will differ in ar-. 
rangement, staining qualities, virulence or other condi- 
tions. The tissues in which a germ is found growing, may 
assist in its identification. As knowledge of bacteria pro- 
gresses, the necessity of not relying upon any one definite 
quality in identification, becomes imperative. Virulence | 
is even more influenced by environment than form. If the 
germ metabolism takes place in the presence of free oxy- 
gen, the toxin may be oxidized and rendered harmless. 
Cholin derived from nerve substance and neurin differ 
only in a molecule of water. One is but slightly pois- 
onous and the other intensely so. When bacteria are able 
to break up the highly organized substances of the human 
body, these atoms at once enter into new combinations 
under the conditions which then exist. Scientists are real- 
alizing the necessity of studying pathogenic germs in the 
environment in which they produce disease. The student 
of malaria goes to the swamp, and the investigator of the 
plague, to Calcutta. In some of the more common germ 
diseases, it is often important that the microscopical ev- 
