944 
Although at this time Ehrlich was especially 
under the direction of the anatomist Waldeyer, he 
rapidly developed a capacity for chemistry which 
was a surprise both to himself and to the chemist, 
Adolf yon Baeyer, whose lectures had been system- 
atically cut by the gifted but unconventional 
student. For unconventional he then was, and ever 
has been, neglecting what he did not like and 
throwing himself with fervor and intense energy 
into the solution of the themes that attracted him. 
From the outset it was clear that Ehrlich would 
make a career as an experimental investigator. 
Much of the time he was supposed to spend in 
taking the usual medical courses he devoted to 
experiment. When Robert Koch was shown 
through the laboratory at Breslau by one of the 
professors, his attention was called to a young 
student working at a desk covered with bottles of 
dyestuffs. ‘‘There is our little Ehrlich,’’ said the 
professor; ‘‘he is a first-rate stainer of tissues, 
but he will never pass his examinations.’’ The 
prediction about the examinations came perilously 
near fulfillment; Ehrlich made bad flunks and it 
is hinted that he never would have received his 
degree had he not made a discovery—namely, the 
existence of the peculiar type of leucocyte which 
is known to us as the ‘‘plasma-cell.’? The faculty 
reasoned that it would be improper to keep so 
promising and original a worker indefinitely in an 
undergraduate position, and it is suspected that 
they mitigated the rigor of the examinations in 
order to relieve their own embarrassment. 
These early studies were doubtless re- 
sponsible for what must be considered as 
the main theme of all Ehrlich’s work—the 
specific affinity which exists between spe- 
cifie living cells and specific chemical sub- 
stances. The ‘‘prepared mind’’ is evident 
in his study of the cells of the blood, of the 
selective action of methylene blue on the 
nervous system, of the use of the same dye 
in the study of oxidation and reductions 
occurring in tissues, of his studies in im- 
munity, of the specific treatment of proto- 
zoan disease, and also according to recent 
reports in his application of the same prin- 
ciple to the study of cancer. Manson’s 
studies of the relation of the mosquito to 
filariasis, which led to Ross’s study of the 
transmission of malaria by the same insect, 
SCIENCE 
[N.S. Vou. XXXV. No. 912 
is another example of the ‘‘ prepared mind’”’ 
properly interpreting a chance observation. 
Sometimes such ‘discoveries are referred to 
as the result of scientific imagination—and 
it truly is this—but doubtless the same 
‘““ehance’’ came to many besides Pasteur, 
Ehrlich, Laveran, Koch, Theobald Smith, 
Manson, Ross and Reed; it was the training 
of these individuals, the mind prepared to 
utilize scientific imagination, that enabled 
them to grasp the opportunity offered by 
““ehance’’ observation. Every one familiar 
with the history of investigation in medi- 
cine knows that before Harvey, men studied 
the circulation; that before Pasteur, bac- 
teria were seen in diseased conditions; be- 
fore Lister, the effect of cleanliness upon 
surgical mortality had been noticed; before 
Laveran, the plasmodium of malaria had 
been seen; before Manson and Ross, the 
possibility of the transmission of malaria 
by the mosquito had been discussed. Truly, 
remarkable achievements are never unique occur- 
rences in nature. Even the greatest men rest on 
the shoulders of a large multitude of smaller ones 
who have preceded them, and epochal discoveries 
emerge out of a period of intellectual restlessness 
that affects many minds.* 
But of these minds, it is that one which 
is ‘‘prepared,’’ trained in the methods of 
observation, therefore possessing the price- 
less quality of scientific imagination, which 
sees the proper block which when placed 
exactly where it belongs completes the edi- 
fice of a perfect theory, and thus estab- 
lishes a new landmark for future progress. 
But what, you ask, has all this to do with 
the training of the physician? How does 
it apply to medical education? We admit 
the value of these qualities in the investi- 
gator, but of what value are they to the 
man seeking the education necessary to 
4Flexner, S., ‘‘The Biological Basis of Specific 
Therapy,’’? Ether Day address at the Massachu- 
setts General Hospital, October 16, 1911. 
