standing.

I will first call the young student's attention to the show of negative
facts (exposure without subsequent disease), of which much seems to be
thought. And I may at the same time refer him to Dr. Hodge's Lecture,
where he will find the same kind of facts and reasoning. Let him now
take up Watson's Lectures, the good sense and spirit of which have made
his book a universal favorite, and open to the chapter on Continued
Fever. He will find a paragraph containing the following sentence: "A
man might say, 'I was in the battle of Waterloo, and saw many men around
me fall down and die, and it was said that they were struck down by
musket-balls; but I know better than that, for I was there all the time,
and so were many of my friends, and we were never hit by any
musket-balls. Musket-balls, therefore, could not have been the cause of
the deaths we witnessed.' And if, like contagion, they were not palpable
to the senses, such a person might go on to affirm that no proof existed
of there being any such thing as musket-balls." Now let the student turn
back to the chapter on Hydrophobia in the same volume. He will find that
John Hunter knew a case in which, of twenty-one persons bitten, only one
died of the disease. He will find that one dog at Charenton was bitten
at different times by thirty different mad dogs, and outlived it all. Is
there no such thing, then, as hydrophobia? Would one take no especial
precautions if his wife, about to become a mother, had been bitten by a
rabid animal, because so many escape? Or let him look at "Underwood on
Diseases of Children," [Philadelphia, 1842, p. 244, note.] and he will
find the case of a young woman who was inoculated eight times in thirty
days, at the same time attending several children with smallpox, and yet
was not infected. But seven weeks afterwards she took the disease and
died.

It would seem as if the force of this argument could hardly fail to be
seen, if it were granted that every one of these series of cases were so
reported as to prove that there could have been no transfer of disease.
There is not one of them so reported, in the Lecture or the Letter, as to
prove that the disease may not have been carried by the practitioner. I
strongly suspect that it was so carried in some of these cases, but from
the character of the very imperfect evidence the question can never be
settled without further disclosures.

Although the Letter is, as I have implied, principal