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POPULAR SCIENCE REVIEW. 
power of gravitation contained in the earth. (2) The lesser influences which 
modify the position it would assume under the influence of that gravitation 
alone are : — (a) the centrifugal force caused by the rotation of the earth on 
its axis ; (5) the power of gravitation contained in the sun and the moon ; 
and (c) the force which acts in opposition to the attraction of the sun and 
the moon. Of these lesser forces the centrifugal force is, like the gravita- 
tion of the earth, fixed and steady. The other lesser influences are con- 
stantly changing their direction, thereby causing that constant changing of 
the position of the water which forms the tides. Such is briefly Mr. 
Jordan’s theory, and we leave it and its author to the consideration of our 
readers. 
CHOLERA TREATED BY ICE * 
T\R. JOHN CHAPMAN, whose efforts to introduce ice as an important 
therapeutic agent, and whose experiments upon the effects of ice in the 
treatment of nervous affections are so familiar to the public and the profession, 
has given us a treatise on Cholera, which certainly deserves notice. We 
shall not say whether, in the present state of our knowledge of the condi- 
tions under which cholera appears, Dr. Chapman is justified in putting 
forward so detailed an hypothesis as that which he advocates, but we must 
confess that, whatever amount of truth it may possess, his view is worked 
out with a display of logical reasoning, formidable facts, and erudition such 
as is seldom met with in medical essays. In noticing the work before us, 
we must do so from two aspects ; we must first consider Dr. Chapman’s 
explanation of the cause of cholera, and, secondly, we must examine into the 
character of his mode of treatment. The first is by far the most interesting 
point. Dr. Chapman thinks that the chief cause of cholera is external heat, 
which, by acting upon the nervous centres, increases the quantity of blood 
supplied to them, and thus brings them more powerfully into action. It 
is known from the experiments of Bernard and other writers that, when 
the sympathetic nerve-centres are stimulated, those of their branches 
supplying the bloodvessels cause these latter to contract. Another 
physiological fact is that, when a secreting surface has its ordinary blood- 
supply slightly diminished, it throws off a larger quantity of fluid than 
usual. Connecting these two well-known laws, Dr. Chapman frames an 
argument somewhat in the following manner : Heat applied to the back 
stimulates the sympathetic nerve ; stimulation of the sympathetic^ causes 
contraction of the bloodvessels of (among other parts) the intestinal canal ; 
the diminution in supply of blood thus produced causes increased secretion 
of mucus, aud finally increased secretion of mucus brings on diarrhoea. 
Thus we see the conclusion is very excellently reasoned out ; but is Dr. 
Chapman quite sure of his premisses ? Has he ever produced true choleraic 
symptoms in animals, let us say, by the application of heat to the spine P 
* u Diarrhoea and Cholera : their Nature, Origin, and Treatment through 
the agency of the Nervous System.” By John Chapman, M.D. M.R.C.P, 
M.R.C.S. 2nd edition, enlarged. London : Triibner & Co. 1866. 
