Proceed nje of ihe Kar.sas C tv AcatU-iny of 
bciencc, J line BUth, !S9l. 
Soiisctliisig" njHtut liiirtciia. 
liV JOSKI'II SllAR!', M. I). 
So nuic'i lias been said alxnit Mico-orpaii 
i^ms as the cause of disease, that we are 
prone 'o think of them only in tnal c<. ni ec- 
tion. Yet this is the very smalhst part 
placed by bacteria in nature. Wh^nevtr 
comp'ex chemical compounds (fSj)ecially 
organic.) are being torn apart, ihey are pres- 
ent. Wherever we have fermeiitation or de- 
cay, it occurs through the agei cy of these 
little bodies. 
It is this phase of tlie question upon which 
I will addrC'-s you this evening or something 
of the natural history of these minute uni- 
celular organisms and their part in the life 
Cycle. 
They are minute vegetable cells very 
small, but because such is the case, we are 
not to presume that we can know nothing 
about them. 
To give an idea of their size, I present this 
diagram, representing ten thousand times 
the diameter of one of the globular forms. 
®1 centimeter, 10,000 times the 
diameter of micrococcus. 
The most useful powers in observation of 
these organisms under the micro.'-cope, are 
those amplifying from 500 to 1000 times, so 
that as actually seen, they appear from 1-10 
to 1-20 of the size here represented. They 
range from .5 micromillimeters to 5. micro- 
millimeters in diameter This diagr.m re- 
presents 10,000 times these dimensions. 
10,000 limes .5 microns the diameter 
of the smaller Bacteria. 
From 11,000 to 44,000 of these minute 
bodies could lie side by side in the space of 
an inch. Miller estimates the Bacteria pre- 
sent in a foul mouth at 1100 millions, or 
about 18 limes tlic pr.scnl i.o|.u!aii.)ii , f i.he 
Uu tetl Slates. - 
No. 3. 
U.OCO limes 5. microns the diainetrr of 
the Luger Bacteria. 
The diameter of a red blood ccjrp' scle of 
man is about 8 microns so that a number of 
bacleiia might fii.d an abiding place in one 
of these cells and they can pass freely through 
the nler.stices of the tissue cells. 
Sir William I'homp^on estimated the di- 
ameter of a molecule at about 1 5 0,000,(00 
of an inch, (.00l.C5 microns.) so ' that every 
one of the minute organisms are an aggrega- 
tion of many thousands of the most complex 
molecules. To those who feel sk^'ptical as 
to the possibility of such estimates being any 
better than wild guesses, it is only necessary 
to cite the making of test plates for the re- 
solving power of microscopes having -^40 to 
893 ) (II ,000 to 224,000 to inch) lines to the 
M i ilinieler I'ukd on glass. 
The limit of microscopic vis'on for ihe 
most useful ol)jective is the resolution of 
about 12l),0fj0 lines to the inch. 
The study of bacteriology then, is ]\ke 
studying the natural history of a valley from 
a neighboring mountain top; only when the 
elements are in the most favorable condition 
will we see anything, and then at first only 
a spot in the landscape, but as we look and 
look, we begin to distinguish general differ- 
* W. D. Miller's .Microorganisms in'thc Human 
mouth. 
