22 
Appin 147H. 
The following paper was read by the President :— 
ON GERMS. 
There is perhaps no topic which has excited greater scientific 
interest and provoked warmer discussions than the so-called Germ 
Theory, or the influence of micro-organisms in the economy of 
nature and the causation of disease. The investigation of the 
infinitely small has always exercised a wonderful fascination over 
the minds of scientists, who ever desire to trace back step by step 
all life to a first cause—a primeval atom—and to follow all the 
tortuous windings of disease until the actual origin is found, the 
first germ, the infinitesimal molecule. Bacteriology, or the study 
of these minute organisms, is, however, too vast a subject to be 
adequately treated in the short space allotted to me. - I marely 
propose this evening to touch upon a few of the more interesting 
points connected with this science, especially as illustrated by the 
discoveries of that great chemist and scientist, M. Pasteur. There 
is no other living man who has done more to benefit society by 
his patient and laborious investigations into the origin of disease, 
which, thanks to his indefatigable zeal, may be said to have 
revolutionised the whole science of medicine and surgery. 
The manner in which M. Pasteur’s labours were directed 
towards this special subject of bacteriology is not perhaps generally 
known, and it is somewhat interesting as illustrative of the homely 
proverb that ‘small beginnings make great endings.” 
Some forty years ago the minds of many eminent chemists were 
greatly exercised by the incomprehensible behaviour of the so- 
called ‘isomeric bodies,’ viz., compounds which, though possessing 
an identical composition, appear, to judge by their chemical action 
and optical properties to be totally different substances. The 
great Swedish chemist Barzelius, and later on Biot, vainly 
endeavoured to solve the problem why two acids which were 
constituted alike had altogether dissimilar properties. I refer to 
the ordinary tartaric acid of wine-lees which possesses the power 
of deviating the plane of polarised light to the right, and a rare 
acid found occasionally in the tartar deposited from wine made in 
the Vosges district, and which is optically inactive. This per- 
plexing question attracted the attention of the then unknown 
Pasteur, and for seven years this indefatigable chemist proceeded 
with his experiments, which were ultimately rewarded with 
success. He discovered that the rare acid itself was made up of 
two compounds which were identical in composition but differed 
