JUNE 21, 1912] 
practise medicine? Let me repeat Pasteur’s 
adage—‘‘In the fields of observation, 
chance favors only the mind which is pre- 
pared.’’ Certainly all will agree that 
medicine is largely an observational science 
and one of the ‘‘fields of observation’’ of 
Pasteur’s definition. Medicine may not be 
all science, but clinical medicine in its most 
essential phase—diagnosis—is essentially a 
science of observation, either of direct ob- 
servation by the use of the unaided senses 
or indirect by the use of instruments of 
precision, or by chemical, biological or 
other tests. Therefore, whatever force or 
whatever lesson this adage may carry, ap- 
plies to medicine. And now as to the inter- 
pretation of ‘‘chance.’’ I have not been 
able to obtain the original French of Pas- 
teur, but from his parenthetical phrase in 
connection with the discussion of the tele- 
graph it is clear that he meant exactly what 
the translator has given us, chance or op- 
portunity in the sense of an unexpected 
observation or an accidental occurrence. 
Pasteur’s idea was that such unexpected or 
accidental occurrences would not arrest the 
attention of the poorly prepared mind, but 
that the well-prepared mind, trained to 
observe, to think and to compare, would 
grasp the significance of the unexpected, 
the unusual or occasional, put the observa- 
tion to the test, by experiment or control, 
and arrive at the correct conclusion. Is 
not this a matter of daily occurrence in 
clinical medicine? Does not chance (op- 
portunity some would call it) and care in 
details play an important part in diagnosis? 
Is not every ailment the physician sees a 
puzzle; every diagnosis, if correct, a solu- 
tion of that puzzle? One speaks of the 
man who solves the puzzle which has baffled 
half a dozen other men, as a keen or accurate 
diagnostician. They imply that he has an 
added power, or that his skill is the result 
of wider experience, forgetting they may 
SCIENCE 
945 
have seen as many individuals with the 
malady as had the consultant, and perhaps 
totally ignorant of the fact that his diag- 
nosis was possibly based on a chance ob- 
servation which meant more to his trained 
imagination than it did to minds unaccus- 
tomed to weigh the significance of details. 
Every clinician of experience can give ex- 
amples of the importance of chance and 
imagination in actual diagnosis. An inter- 
esting illustration is that 
of the two students who reported on the same 
patient in competition for a clinical prize. The 
patient presented, among other symptoms, a re- 
markable discoloration of a certain area of skin, 
and the first student described this discoloration 
with the most careful minuteness. He measured 
it in different directions and drew a rough sketch 
of its general outline. The second observed the 
phenomenon with equal care, but he exercised his 
imagination and formed a hypothesis which he pro- 
ceeded to put to the test. He asked a nurse for a 
wet towel, with which he wiped the discoloration 
away. It is evident that the faculty which he thus 
brought to bear on the problem before him would 
be likely to stand him in good stead in relation to 
many others of a more complicated character; and 
that his exercise of the art of diagnosis would be 
practically immune from the errors incidental to 
the habit of taking all appearances at their face 
value. Imagination at once points to the possi- 
bility of more than one explanation of any given 
occurrence, or alleged occurrence, and compels 
inquiry as to the existence of probable causes 
beyond the particular one which may at first sight 
appear to have been in operation.” 
From what has been said, then, it should 
be evident that it is the first duty of a med- 
ical school to prepare men properly for the 
practise of medicine (and the most ardent 
advocate of research in the university will 
not deny that this is the first duty). If so, 
what are, conditions to be fulfilled to ensure 
the ‘‘prepared mind’’ of Pasteur’s adage? 
The Preliminary Education of the indi- 
5¢<Tmagination in Medical Research,’’ Lancet, 
1912, CLXXXII., 179. 
