286 
POPULAR SCIENCE REVIEW. 
surface of the ground along the line of such section is not accurately- 
represented. 
The last two chapters contain (1) the practical application of geological, 
surveying, involving the methods and operations described in the preceding 
pages, and (2) the way in which geological knowledge and reasoning may 
be turned to account with regard to the supply of water and the origin and 
character of soils. 
The book is a useful addition to geological literature, and no earnest 
student of the science should fail to consult it, and carry out in the field the 
instructions contained in its pages, which the author has rendered as concise 
as possible, in order to facilitate the acquirement of a knowledge of field 
geology, and to embody in a small compass practical directions and 
suggestions which are to be found only here and there in more important 
works. 
THE GERM-THEORY OF DISEASE.* 
T HE author of this very ingenious book explains contagion and the course 
of fevers by the theory of special germs being introduced from without 
into the body. u The theory is, that many diseases are due to the presence 
and propagation in the system of animal organisms having no part or share 
in its normal economy. This it is, and no more. It is essential to be clear 
on this point ; for the opponents of the germ-theory, and, to some extent, its 
advocates also, have introduced into the discussion of that theory the ques- 
tions of the source and mode of origin of these organisms — a complication 
which has tended to hamper men’s minds and to divert attention from the 
real subject of discussion — the competence of germs to produce the phenomena 
of disease .” The morbific agent propagated in and given off from the bodies 
of the sick — a contagium — may gain entrance into other bodies through the 
lungs or the alimentary mucous surface. This is an organic body too small 
to be seen except through the agency of the electric beam, and which pro- 
pagates in the blood and acts as a parasite. The shiver of fever is produced 
by a sudden and enormous development of the germs, and the non-elimina- 
tion of urea to their demanding nitrogen. Just as micrococci are visible in 
the tissues affected by diphtheria, so these infinitely small germs do equiva- 
lent mischief. We must hope for some new treatment which will settle 
these germs, and until that is discovered we must be in the same condition 
as we were in our beliefs thirty years ago, when Southwood Smith decided 
that fever was from want of oxygen, and because salt made the fever-blood 
red and arterial-looking, salted, and sometimes cured his patients. As a 
matter of fact, did not Sir Henry Holland elaborate the germ-theory thirty 
years ago ? 
The book is well worth reading, and is sufficiently free from professional 
technicalities, so that it may be read by the public with advantage. 
* 11 The Germ-Theory Applied to the Explanation of the Phenomena of 
Disease. The Specific Fevers.” By T. Maclagan, M.D. 8vo, London:. 
Macmillan. 1877. 
