360 
AEFREI) L. LOOMIS. 
of disease. This latter theory so readily explains many of the 
facts connected with the development and reproduction of infec¬ 
tious diseases that it has been unqualifiedly adopted by a large 
number of investigators. The proofs of this theory had not^ 
however, advanced beyond the demonstration of the presence of 
certain forms of bacteria in the pathological changes of a very 
limited number of infectious diseases, until February, 1882, when 
Koch announced his discovery of the tubercle bacillus, since 
which time nearly every disease has its supposed microbe, and the 
race is indeed swift in which the would-be Kochs press forward 
with new germs for public favor. 
It is my purpose this afternoon to pass in rapid review the 
subject of Bacteriology, noting first the different genera, their 
biology, etc., and the modern means employed in their study. In 
referring to the practical study of our subject, I shall do little 
more than describe very briefly the processes as employed in our 
own laboratory of biology. Here you will find every means 
for investigating this subject, and I hope you will avail yourselves 
of the facilities offered for practical work. 
The term bacteria , or microbe, refers to minute particles of 
matter, microscopic in size, which belong to the vegetable kingdom, 
where they are known as fungi. If we examine a drop of de¬ 
composing urine under the microscope, amplifying say four 
hundred diameters, the field is seen swarming with minute bodies, 
some mere points, others slightly elongated into rods, all in active 
motion, rising, falling, oscillating—a ceaseless confusion. If the 
water be allowed to evaporate, all becomes still, and the slide 
seems covered with mere dust. Apply a drop of water, and 
after a short time the little, dried-up granules again show their 
activity, as though nothing had intervened to disturb their 
vocation. Similar minute forms are seen in every decomposing 
fluid, often in the blood and sputum of healthy persons. The 
air is full of them ; the dust of our dwellings abounds with their 
spores in countless numbers, only awaiting suitable conditions to 
start into active and rapid reproduction. As I have said, certain 
forms are found in the blood of healthy persons, while other 
forms are found in the blood of disease. 
