50 NATURE 

being exposed to polarised light, one to ordinary 
light, the third being kept in darkness, After thirty 
to sixty minutes, depending on the strength of the 
diastase, rapid hydrolysis can be seen to take place 
on the slides exposed to polarised light, while in 
the two controls the starch granules remain almost 
intact for some hours. By the use of a delicate 
thermocouple, the temperature was proved to be 
the same in all three cases. When the light is 
intense, the starch granules in the case of the polarised 
light break down entirely to little masses of dextrin 
and crystals of sugar which give deposits of cuprous 
oxide on warming with Fehling’s solution. These 
results have been obtained with potato starch and 
the endosperm of maize and of wheat, the latter 
without the addition of diastase if freshly prepared. 
In view of the suggestiveness of these observations 
the investigation is now being extended in various 
directions, and I hope to communicate the results in 
due course. ELizABETH SIDNEY SEMMENS. 
Chemical Laboratories, 
University of Liverpool, 
December 16, 
Medical Education. 
REFERRING to my letter (NATURE, December 9, 
p. 769), Prof. Dakin writes (NATURE, December 23, 
p. 845): ‘“‘ lam not quite clear whether this question 
has been propounded to invite answers, or to intro- 
duce another of Sir Archdall Reid’s favourite discus- 
sions on mutations and fluctuations, etc.’’ Prof. 
Dakin may rest assured that I do not invite a discus- 
sion about mutations and fluctuations. To be frank, 
I do not think such a discussion, conducted on 
purely scholastic lines, out of touch with reality, 
would be profitable. My object was simply to 
protest against the waste of time to which, as I 
supposed and still suppose, unhappy medical students 
are compelled. Here are some truths, none of which, 
I think, Prof. Dakin will deny categorically, but all 
of which, in practice if not in theory, are repudiated 
by many teachers of biology. 
(x1) Every relevant and verifiable fact, no matter 
how observed, is equal before science. Experiment 
is only one way—a very good way when need arises 
—of observing. The vast majority of authentic 
facts about living beings is derived from direct 
observation. People who limit their data to facts 
derived from experiment, or any other mode of ob- 
serving, are, like those who insist on purely Christian, 
Mahomedan, or Hindoo testimony, merely sectarian. 
Dwelling in an islet of evidence they ignore the con- 
tinent of truth which lies at hand. 
(2) Our powers of observing are proportionate to 
our familiarity with the objects of study. Thus we 
can scarcely differentiate between peas in a pod or 
sheep in a flock; to an Englishman newly arrived 
in China all the natives seem much alike; but 
among our own kind, whom we study from birth to 
death, especially among our intimates, we see differ- 
ences of every shade (7.e. fluctuations) between vital 
and enormous extremes—as, for example, in powers 
of resisting disease. Obviously, the experimenter 
who works among plants and lower animals knows 
nothing about fluctuations, and less than he ought 
to know about mutations. Lacking the necessary 
powers of observation, he merely guesses. That he 
guesses wrongly was abundantly demonstrated by 
my letter. 
Can Prof. Dakin deny (a) that men, the only living 
beings minutely observable, are subject to stringent 
natural selection, (b) that this selection occurs amid 
NO. 2776, VOL. I11| 



[JANUARY 13, 1923 
fluctuations, (c) that evolution, proportionate to the 
length and severity of the selection, has resulted, 
(d) that human races never differentiate while there 
is interbreeding, but differentiate rapidly and in- 
variably when separated by time and space, (e) that 
human races blend perfectly when crossed except 
in traits linked with sex, (f) that in spite of multi- 
tudinous human racial differentiations, there has 
never yet been recorded a useful human mutation, 
or one that changed the type of a race, (g) that 
human mutations (e.g. club-feet, idiocy, albinism) 
are not inherited independently, but are only repro- 
duced independently, and (hk) that lost ancestral 
traits never appear among natural varieties, but 
frequently among artificial varieties, even when 
purely bred. 
Unless a biologist is able (1) to accept the 
foregoing propositions, or (2) ‘to disprove them, or 
(3) to demonstrate that man is outside the scheme 
of Nature, he is not competent to teach biology to 
medical students ; for, after these students leave him, 
they will observe for themselves, and be taught by 
men who have observed, with a minuteness and 
accuracy impossible to workers among plants and 
lower animals, and the things they then learn will be 
directly contrary to the teachings of the biologist. 
I have before me the synopsis of instruction in 
biology of the Royal Colleges of Physicians and 
Surgeons. I must admit that it is a vast improve- 
ment, chiefly by way of elimination, of the rubbish 
(for a medical man) that I was taught as a student 
and which I supposed was still taught. The 
syllabus for 1923 will be even shorter and better. 
Biology, which should make doctors, in their vast 
numbers, the most potent scientific influence in 
the community, is disappearing from the curriculum, 
But I observe that the student must still learn the 
general structure of the Hydra and Lumbricus, the 
general structure and elementary physiology of 
Scyllium and Rana, and the elementary facts of 
evolution, heredity, and variation. But of what 
use, as taught by biologists, can these subjects be to 
the medical student ? What, for example, will he 
learn about evolution, heredity, and variation ? 
Will he learn that some characters are “‘ innate,” 
and the rest “‘ acquired ’’ ? Recently I spent eighteen 
months trying to find out what biologists meant 
by these words and none could tell. Will he learn 
from a Lamarckian teacher that acquired characters 
are inherited, or from a neo-Darwinian that they 
are not ? I spent a like period in trying to find out 
what was meant by “inherited,” and failed again. 
Will he learn from a Darwinian that fluctuations 
furnish the materials for evolution? Or from a 
Mutationist that only mutations do so? Or will 
he be presented with such statements as the following : 
“The standard deviation of a coefficient of correlation 
computed from data derived from classes, members 
of which are mutually correlated, with special refer- 
ence to the case of fraternal and parental correlations 
calculated from entries of siblings” ? Will any 
biologist tell him that every character is a product 
of the combined action of nature and nurture (that is, 
is equally innate and acquired), that the human 
being is of such a nature that he is especially respon- 
sive to the nurture of use, and that this peculiarity 
bestows on man his position in the scale of life and 
has made him the educable and therefore, according 
to the teaching he receives, the rational animal— 
able to learn, for example, sense or nonsense concerning 
biology. 
9 Victoria Rd. South, 
Southsea, Hants. 
December 26. 
G. ARCHDALL REID, 
a 
