6G The Microscopic Germ Theory of Disease. By H. G. Bastian. 
these, I regret to say, have proved insufficient to enable me to 
bestow the attention I should have desired upon the vast accumu- 
lation of writings directly or indirectly related to the subject 
selected for discussion, and quite insufficient also to enable me to 
throw light upon it, to the extent I should have wished, by certain 
new observations of my own. The subject, however, large as it is 
— and consequently difficult to be dealt with satisfactorily in the 
space of one hour — seemed to recommend itself for several reasons : 
(1) It is a question lying at the root of the pathology of the most 
important and most fatal class of diseases to which the human race 
is liable — diseases which cause nearly one- fourth of the total number 
of deaths in this country. (2) It is a subject important alike to 
those engaged in almost every department of our profession. And 
(3) it is one which I happen to have very carefully considered for 
several years, and for the elucidation of which I was tempted in 
1869 to undertake long and laborious investigations, though these 
may have seemed to many to have little practical bearing upon the 
science of medicine. 
The subject of the relation of the lower organisms to disease 
has, moreover, a growing importance. The notion that there is a 
distinct causal relation between the two — though it has long existed 
in one form or another — is one which has been spread enormously 
within the last few years, partly owing to our increase of knowledge 
concerning these low organisms, and partly because of their ascer- 
tained presence in numerous diseased tissues and exudations. 
Medical hterature both at home and abroad, now, in fact, teems 
with papers and memoirs bearing upon this relation, and such 
communications rapidly increase in number year by year. 
In the short time allotted to me to open the debate, I shall be 
able to make specific allusions to but few of these contributions, as 
it would seem better to keep the broad issues well in view in my 
opening statement, and reserve questions of detail, as these may be 
taken up by other speakers and subsequently commented upon if 
necessary. 
The one common and distinguishing feature peculiar to all the 
diseases whose pathology we are now about to consider is their 
“ contagiousness.” An individual affected by either of them throws 
off’ particles from the region specially affected, or from many parts 
of the body, and these particles, on coming into contact with suit- 
able surfaces in other persons, may incite similar local or general 
diseases, though such results do not invariably follow. This pecu- 
liarity, by means of which such diseases are spread amongst the 
members of a community, was, even in the time of Hippocrates, 
compared to the property by which one fermenting mass may 
communicate its state of change to another mass of fermentable 
