the bacilli. There are other forms which bacteriologists have dubbed
with similar descriptive names, but they are more interesting to the
physician than to the surgeon. Many micro-organisms, whether cocci,
bacilli, or of other shapes, are harmless, hence they are called
non-pathogenic, to distinguish them from the disease-producing or
pathogenic germs.

As many trees have the same shape and a similar method of growing, but
bear different fruits--in the one case edible and in the other
poisonous--so, too, bacteria may look alike to the microscopist's eye,
and grow much in the same way, but one will cause no disease, while
the other will produce perhaps tuberculosis of the lungs or brain.

Many scores of bacteria have been, by patient study, differentiated
from their fellows and given distinctive names. Their nomenclature
corresponds in classification and arrangement with the nomenclature
adopted in different departments of botany. Thus we have the
pus-causing chain coccus (streptococcus pyogenes), so-called because
it is globular in shape, because it grows with the individual plants
attached to each other, or arranged in a row like a chain of beads on
a string, and because it produces pus. In a similar way we have the
pus-causing grape coccus of a golden color (staphylococcus pyogenes
aureus). It grows with the individual plants arranged somewhat after
the manner of a bunch of grapes, and when millions of them are
collected together, the mass has a golden yellow hue. Again, we have
the bacillus tuberculosis, the rod-shaped plant which is known to
cause tuberculosis of the lungs, joints, brain, etc.

It is hardly astonishing that these fruitful sources of disease have
so long remained undetected, when their microscopic size is borne in