LECTURE ON BACTERIOLOGY. 
359 
LECTURE ON BACTERIOLOGY,* 
DELIVERED IN THE MEDICAL DEPARTMENT OF THE UNIVER¬ 
SITY OF THE CITY OF NEW YORK, OCTOBER 14, 1885. 
By Alfred L. Loomis, M.D., LL.D. 
Gentlemen : Before commencing the history of the so-called 
infectious diseases, I will invite your attention to a brief consider¬ 
ation of those low forms of life which have become known to 
our every-day literature as Bacteria. The scientific world is at 
present devoted to their study, and it is a subject of especial 
importance to us in commencing our studies of the etiology of 
the class of diseases which are about to engage our attention. 
If bacteria are active elements in the production of patholog¬ 
ical conditions, their biology becomes a matter which must 
concern every progressive medical investigator. If, on the other 
hand, as many are inclined to believe, they have little or noth¬ 
ing to do with the causation of disease, it equally becomes us as 
intelligent men to investigate, and if possible, determine their 
real significance. At different periods in the history of medicine 
different theories have been advanced, and for a time have held 
the minds of the profession, to account for the causation of dis¬ 
ease, as well as for the peculiar phases which it assumes during 
its active progress. 
There are at present two prominent theories in regard to the 
infections which produce disease. The first is based upon 
chemical processes; the second upon the multiplication of living 
organisms. The chemical theory maintains that after the infec¬ 
tious element has been received into the body it acts as a ferment, 
and gives rise to certain morbid processes, upon the principle of 
catalysis. The theory of organisms, or the germ theory, main¬ 
tains that the infectious elements are living organisms, which, 
being received into the system, are reproduced indefinitely, and 
excite morbid processes which are characteristic of certain types 
Reprint from the Medical Record. 
