72 TRANSACTIONS. OF THE 
tissue. Hence the putrefactive changes which occur in 
wounds and after operations on the human subject, from 
which blood-poisoning and gangrene so often follow, might 
be absolutely prevented if the injured surfaces could be 
kept from the germs of decay. So he began experimenting 
to find a drug that would kill the germ without injuring the 
patient. As we know, the results of his experimentation 
were crowned with success. 
I need not discuss further the investigations which 
have led to the development of the science of Bacteriology. 
Francisco Redi’s simple experiment has borne a wondrous 
fruitage. We realize the important role played by bacteria 
not only in medicine, but in agriculture as well, where they 
cause destructive plant diseases, aid in fertilizing the soil, 
and give characteristic flavors to various products. 
But not only in a true understanding of the nature of 
bacteria has the explosion of the Spontaneous Generation 
theory aided medical science. 
In 1833 an English medical student noticed little glist- 
ening specks in the muscular tissues of a human subject. His 
professor of comparative anatomy classified them as being 
the cocoon of a minute “insect”, and gave it the name of 
Trichina spiralis. In 1847, the cysts of Trichina were 
found in pork by the American anatomist, Dr. Joseph 
Leidy. Some time elapsed before the life cycle of the 
Trichina had been worked out by German zoologists. This 
discovery stimulated investigation as to the part played by 
animal parasites in diseases of the human body. One of 
the most striking cases of animal parasitism has only re- 
cently been brought to light as occurring in the United 
States; only recently, I say, notwithstanding the fact 
that it affects over two million people: Affects, did I say? 
Rather, it makes them useless citizens, with life a burden 
to themselves. I refer to the hook-worm disease, discovered 
in May, 1902, by Charles Wardell Stiles. At the time of 
the announcement of his discovery Dr. Stiles was a zoolo- 
gist at the Bureau of Animal Industry, Washington. In 
December of the same year Dr. Stiles addressed the Pan- 
American Sanitary Congress on the subject of his discovery. 
