170 
NATURE 
[APRIL 15, I915 

twenty minutes or so, the condition of scotopia 
or twilight vision is developed, in which the 
retinal sensibility is enormously increased; it will 
now be found that if the illumination be very low 
the eye is absolutely colour blind. The curve of 
luminosity in such an achromatic scotopic eye is 
practically identical with the luminosity curve of 
the spectrum in any colour-blind person (p. 53), 
the brightest part of the spectrum being near the 
E line (530 pp) instead of near the D line (580 pp) 
as in the normal eye. 
The phenomena of simultaneous and successive 
contrast and fatigue are dealt with in pp. 100—- 
129, and then there follows an interesting account 
of the researches on the discrimination of colour 
by various animals and by primitive races. Con- 
clusions about both of these must necessarily be 
indefinite. With regard to the latter, the mural 
decorations of ancient Egypt show that the sense 
of colour for red, yellow, green, and blue was 
well developed five or six thousand years ago. 
Limits of space forbid a review of Part iil. on 
the various theories of colour vision: the duplicity 
theory—that the cones are the seat of impulses 
that lead to colour perception, while the rods are 
only influenced by light stimuli; the three com- 
ponents theory (Young, Helmholtz); the three 
opponents theory (Hering); and seven other 
theories are described and criticised with justice 
and judgment. The author is to be congratulated 
on- producing a work that contains an immense 
amount of information with a good bibliography 
on ‘the subject. 
general and unbiassed view 
theories of colour vision. 
He has given us an excellent 
of the facts and 

THE EXPERIMENTAL METHOD IN 
MEDICINE AND SURGERY. 
Animal Experimentation and Medical Progress. 
By Prof. W. W. Keen. With an introduction 
by Dr. Charles W. Eliot. Pp. xxvi+ 312. 
(Boston and New York: Houghton Mifflin 
Company, 1914.) Price 7s. 6d. net. 
iE America there are very few surgeons more 
eminent, more beneficent, or more widely 
beloved than Prof. Keen. He fulfils and repre- 
sents the very highest traditions of American 
surgery. He has done great things in practice, 
and in teaching, and in writing; and his name is 
held in reverence by doctors and surgeons over 
here. So, when he writes a book for general 
reading on a medical subject, the general reader 
had better read it: especially as it has an intro- 
duction from Dr. Charles W. Eliot, sometime 
president of Harvard University. Besides, the 
book is admirably written, full of learning, full 
NO. 2372, VOL. 95] 

! 

of sympathy, full of a thousand facts touching 
man’s daily welfare. 
It is a justification, and more than justification, 
of experiments on animals for the advancement 
of the science and art of medicine and surgery. 
Prof. Keen is one of those leaders of his profession 
who are very sensitive to the brutal abuse and 
false witness of the ‘“anti-vivisectionists.” 
Whether it is wise’ to care so much what they 
say, each man must settle for himself. Anyhow, 
Prof. Keen does care very much indeed. He 
takes it to heart that these wild people are set 
to insult the medical profession, to give the lie 
to plain facts, and to attack with virulent language 
the very methods which they themselves take 
advantage of when they are ill. These people seem 
to be just as unkind and untruthful in America 
as they are here. Indeed, we are having a rest 
from them here, since the war began; except that 
some of them are trying to stop our soldiers from 
being protected against typhoid fever. It will be 
a grand thing, after the war, if we can keep anti- 
vivisection down, and give ourselves to worthier 
pursuits. 
The book is a collection of essays, from 1885 
to 1913, on the debt which mankind and the 
animal world owe to experiments on animals; and 
on the character and the attitude of anti-vivisec- 
tion. The essays are complete, final, authorita- 
tive; they are the work of a master of surgery, 
a leader among surgeons. Where all are good it 
is hard to prefer one before another. Among 
those essays which review the benefits gained 
from experiments on animals, nothing could be 
better than “Recent Progress in Surgery,” “ Vivi- 
section and Brain-Surgery,” and “What Vivi- 
section has done for Humanity.” Among those 
essays which review the moral obliquity of anti- 
vivisection, nothing could be better than “The 
Influence of Anti-vivisection on Character,” and 
“The Anti-vivisection Exhibition in Philadelphia 
in 1914.” These two essays are masterpieces ; 
they are gentle, quiet, courteous; but they expose 
a state of mind, in some American women, which 
is not pleasant to contemplate. Things were bad 
enough here, up to last August; but they seem 
even worse in New York. 
Indeed, that is one of the strongest arguments 
against anti-vivisection—that it tends, unless it 
be held under self-control, to such amazing dis- 
honesty, such greedy willingness to believe evil 
of other men, such loss of the sense of responsi- 
bility and of restraint. 
But these faults, after all, are not the main 
theme of the book: and the work of nailing lies to 
counters is less important to us than the work of 
| setting forth the great discoveries of medical and 
