NATURE 
605 
THURSDAY, AUGUST 13, 10914. 
AGRICULTURAL BACTERIOLOGY. 
Vorlesungen itiber landwirtschaftliche Bakterio- 
logie. By Dr. F. Loéhnis. Pp. viii+ 398+x 
plates. (Berlin: Gebriider Borntraeger, 1913.) 
Price 16 marks. 
ODERN research has established the mani- 
fold activities exerted by micro-organisms 
in almost every department of agriculture and the 
attention of micro-biologists has naturally been 
directed to a study of the micro-organisms present 
in soil which influence its fertility, and of those 
met with in fodder and manure and in agricultural 
products such as milk, butter, and cheese. The 
result has been that many books dealing with 
these subjects have appeared during the last few 
years, but we doubt if any single volume has been 
issued which will compare with that under review 
in the completeness with which agricultural bac- 
teriology is treated in a comparatively short space 
of five and twenty lectures. Prof. L6hnis has 
managed to convey an admirable summary of the 
whole subject. 
The volume commences with an excellent his- 
torical introduction which the author directs 
attention to papers by E. King, published in 1693, 
in the Philosophical Transactions of the Royal 
Society, London (vol. xvii), which seem to have 
been overlooked and which confirm and extend 
the observations of Leeuwenhoek on the presence 
of micro-organisms various organic fluids. 
The second and third lectures deal with the general 
morphology, classification, and nomenclature of 
the bacteria. The author adopts practically the 
old Zopf classification, remarking that no better 
one has yet been formulated; with this we cor- 
dially agree. Succeeding lectures deal with the 
biology, cultivation, and investigation of micro- 
organisms, the circulation in nature of nitrogen, 
carbon, hydrogen, and oxygen, exchange and de- 
composition of mineral salts, and the pathogenic 
functions of micro-organisms, and this completes 
the first part of the volume. The second part 
deals with micro-organisms present in fodder, 
milk and milk products, manure and soil, and the 
changes which they produce. In this we find 
accounts of the cellular elements in milk, the 
heating of manure and hay, nitrification, the pos- 
sible influence of protozoa and of “toxins” in 
the soil on fertility, and the use of artificial bac- 
terial fertilisers. In the last Connection we miss 
any reference to Prof. Bottomley’s investigations. 
The volume is excellently printed and produced, 
and the illustrations form a striking feature. 
There are ten plates, of which eight are coloured 
NGwe2 437," VOL. ga | 
in 
in 
and admirably depict the objects represented, 
one of the most successful perhaps being that of 
a sole glowing with phosphorescent bacteria, a 
most difficult subject to reproduce. There are 
sixty figures in the text, some of which are novel. 
By depicting a rectangular jar of given size wiih 
a small black square in it drawn to scale an idea 
is given of the volume occupied by a certain 
number of bacteria compared with the volume ot 
the material in which they occur, such, for ex- 
ample, as milk. Rei se 
THE. *CONSTITULION® ORY cALiOY S. 
Metallographie. By Dr. W. Guertler.  Erster 
Band: Die Konstitution. .Erster Teil. Heft 
i_xii. Pp. 1177. (1909-1912. Zweiter Teil.) 
Heft. i., Die Konstitution des Systemes Eisen- 
Kohlensto ff der sonstigen  bindren 
Kohlenstofflegierungen. Pp. xl+648+ plates. 
(Berlin: Gebriider Borntraeger, 1913.) Price 
32 marks. 
SOWLEe 
HE scientific study of alloys has attracted a 
whole host of investigators during the last 
twelve years, and the mass of experimental 
material has increased with great rapidity. 
Metallography has become a distinct branch of 
applied physical chemistry, having numerous con- 
with mineralogy and with engineering 
science. There are many text-books dealing with 
the principles of metallography or with its appli- 
cations, but the work now in course of publication 
by Dr. Guertler has a much wider scope. It aims 
at being a complete treatise on the subject, review- 
ing critically both methods and results, and also 
serving as a work of reference. The practical 
methods of thermal analysis, micrographic ex- 
amination, etc., and the physical properties of 
alloys, are left for discussion in iater volumes, and 
the volumes now published deal only with the 
equilibrium of phases in alloys. The general ex- 
planation of the meaning of the equilibrium dia- 
gram has been written with the object of making 
such diagrams intelligible and useful to the techni- 
cal metallurgist, who may not be acquainted with 
the principles of physical chemistry. This general 
account is very clearly written, but the number of 
new terms introduced, and the rather complicated 
illustrations of possible forms of equilibrium, may 
repel some such readers. The discussions of such 
subjects as diffusion and incomplete equilibrium 
are excellent. 
Just one-half of the first of the present volumes 
is occupied by a detailed account of binary alloys, 
classified according to a modified periodic system. 
Even then, the alloys of the calcium and alumin- 
ium groups are postponed to a later section, 
B B 
tacts 
