70 NATURE 

although he has had and still has detractors, the vast 
mass of opinion of those most entitled to form a judg- 
ment of its merits would be in agreement with that of 
the learned August Hirsch, that “ it can only be folly 
or stupidity that would seek nowadays to minimise or 
to question the immortal merits of Jenner.” 
When Jenner died Louis Pasteur was a month-old 
babe. Thus two great lives were linked : one immortal 
for a single great empirical discovery, the other destined 
to carry on the torch and found a science. It is doubt- 
ful if even yet the precise relationships of smallpox to 
cowpox are fully understood, in spite of the great mass 
of experimental work devoted to the problem during the 
past hundred years, nor can we point to any great 
advance in knowledge of the exact nature of the viruses 
concerned. Opinion, however, has quite definitely 
crystallised on one point, namely, that cowpox—now a 
great rarity in nature—is no spontaneous disease of the 
cow but is simply the bovine response to accidental 
infection with smallpox virus or vaccinia, conveyed by 
the hand of the milker. The evidence on which this 
statement is based rests fairly securely (1) on the 
successful results of experimental transference of 
variola to the cow, (2) the benign nature of the resultant 
lesions, and (3) the undoubted immunity to smallpox 
which the bovine disease confers when retransferred to 
man. It is true that, in the past century, schools of 
dualists and unicists have engaged in acrimonious 
discussion, but the spoils of the battle rest with the 
latter. Cowpox or vaccinia is simply an attenuated 
form of smallpox, and were there no smallpox there 
would be no naturally occurring cowpox. Further, 
with none of the other eruptive lesions in the domestic 
animals (horse-pox, sheep-pox, etc.) can smallpox be 
brought into similar relationship. These others are 
independent infections. 
The diversity of response to one and the same virus 
by various animal species has been a fruitful field of 
speculation since Pasteur’s time, and we know that 
Pasteur’s chief concern was to expand Jenner’s dis- 
covery so as to secure, for immunisation purposes, some 
strain of other living viruses, which, with the property 
of virulence removed or at least depressed, would yet 
adequately perform the function of immunising against 
the fully virulent variety. In swine erysipelas, Pasteur 
claimed to have secured the desired attenuation by 
passage through another species—a result on all fours 
with Jenner’s observation as we now understand and 
interpret it. These normal immunities and explana- 
tions of them will doubtless for long be the subject of 
research, and in the present issue we take the oppor- 
tunity of reprinting the main part of a recent address 
by Prof. J. C. G. Ledingham, who discusses the present 
state of knowledge in relation to normal immunity of 
NO. 2777,.¥OL. 111] 
[ JANUARY 20, 1923 
species to various infections, and the factors on which 
such immunities have been alleged to depend. 

Science in Secondary Schools. 
HE committees appointed to consider the position 
of Natural Science, Modern Languages, Classics, 
and English in the educational system of Great Britain 
have now formulated their reports, and the Board of 
Education has issued a circular (No. 1294, December 6, 
1922) in which some of the consequences of these 
reports are discussed. One of these is the question of 
the amount of time to be given to the teaching of 
individual subjects, and as the result a time-table has 
been provisionally drawn up which provides for 35 
to 37 teaching periods of 45 minutes each per week 
in school, and not including time necessary for exercises 
and preparation. The Science Committee considers that 
not less than six periods per week should be given to that 
subject. This means about three-quarters of an hour per 
day, and no science teacher will be disposed to consider 
that too much for boys between the ages of 13 and 16. 
The main point for consideration relates to the 
subjects which should be taught in the course of the 
school life, say altogether eight or nine years. As 
usually arranged, the course begins with nature study, 
followed by physics and chemistry, and no time is 
provided for subjects like astronomy and the elements 
of geology, which are necessary for the apprehension — 
of common terrestrial phenomena. In considering 
such a question, regard should be had to the objects 
to be kept in view in teaching natural science at 
school. The first consideration should not be the 
usefulness of the applications of science, but its purpose 
should be to furnish the mind and supply some kind 
of clue to the phenomena of the physical world into 
which man is introduced at birth. 
It is further necessary to cultivate habits of attentive 
observation and careful reasoning, so that some at 
least of the delusions to which all are exposed should 
be less deadly. It is, however, not necessary or 
desirable that all the subjects referred to should be 
taught at the same time, and they need not be taught 
with the same degree of thoroughness. Much general 
information may be imparted in a well-chosen series 
of lessons in nature study, while chemistry and physics, 
begun later, should be carried on to the end of school 
days. Many illustrations of facts relating to other 
subjects may be introduced in a less formal manner, 
not as school lessons but with the aid of the lantern 
and a sort of popular lecture, not to be followed by 
any examination or other test which only frightens 
young people away. ; 
The circular from the Board of Education contains 
the remark that with “ four periods of 45 minutes in the 
