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XII.— THE USE OF THE MICROSCOPE IN THE 
BREWING INDUSTRY. 
By A. Chaston Chapman, Pres.I.C., F.R.S., E.R.M.S. 
( Read June 21, 1922.) 
In no industry, perhaps, lias the use of the microscope for research 
and for control purposes been directly responsible for greater 
technical advances, and indirectly for more far-reaching discoveries, 
than in brewing. Although the brewing of beer is one of the most 
ancient of the industrial arts, it was not until the year 1876, when 
Pasteurs classical work “ Etudes sur la Biere ” appeared, that 
crude and often costly empiricism gave way to scientific method 
and control in this and other fermentation industries. As the 
results of his investigations Pasteur was led to the conclusion that 
many of the “ diseases ” to which beer was liable were caused by 
micro-organisms other than yeast, and he embodied that conclusion 
in two famous sentences : — 
( a ) “ Every unhealthy change in the quality of beer coincides 
with the development of micro-organisms foreign to brewer’s yeast, 
properly so-called.” 
( b ) “ The absence of change in wort and beer coincides with 
the absence of foreign micro-organisms.” 
These two sentences may be taken as marking the transition 
from empiricism and chaos to science and order in brewing opera- 
tions. 
Although extended and modified as the result of subsequent 
research, they may be regarded as the foundation stones on which 
much of modern brewery practice is built, and without which real 
success, if attained at all, would be largely a matter of chance. 
Inasmuch as souring and some other of the more striking changes 
which occur when beer undergoes deterioration are due to the 
activity of bacteria, it was not unnatural that Pasteur’s attention 
should be very largely concentrated on organisms of that class. 
He did not, as a matter of fact, overlook the possibility that certain 
of the yeasts might be technically pathogenetic, but it will be 
obvious that no definite information on this point could be forth- 
coming until some means had been devised for preparing them in 
pure culture as a preliminary to a study of the technical characters 
of the various species of organisms which at that time constituted 
“ brewer’s yeast, properly so-called.” This achievement was due 
to the Danish biologist Hansen, who in 1879 showed how any 
