July 14, 1923] 



NA TURE 



49 



an Englishman in 1776 and a German in 1918 till 

 November 11." Obviously it is impossible to place 

 such teaching in the Christian scheme. But we do 

 not see how it can be reconciled with the position 

 which Prof. Hopkins finally reaches. " Whether 

 called divine or not, one controlling conscious in- 

 telligence appears to exert its will towards the realisa- 

 tion of a moral ideal in which we participate." It 

 seems to us that, if the implications of this conclusion 

 are developed, the main postulates of Christian Platon- 

 ism must be accepted. Such, at any rate, is the con- 

 tention of some of our foremost English theologians. 

 Men of science, interested in these matters, should 

 study the Confessio Fideivihxch. appears at the beginning 

 of the second series of Dean Inge's " Outspoken Essays." 

 They will find there no scientific obscurantism, and, 

 at the same time, a powerful discrimination between 

 the ethico-religious values of theism and pantheism 

 which Prof. Hopkins might study with advantage. 



E. W. Barnes. 



Bacteria of the Soil. 



Agncidtural Bacteriology. By Prof. J. E. Greaves. 

 Pp. 437. (London : Constable and Co. Ltd., 1922.) 

 215-. net. 



WITH the large increase in agricultural experi- 

 ment stations throughout the world, and with 

 the growth in size and activity of such older stations as 

 Rothamsted within the last ten years, there has been 

 produced a vast amount of work dealing with the 

 activities of bacteria in the soil, their relations to soil 

 fertility, and the influence upon them of external con- 

 ditions such as manurial treatment. Much of this work 

 is disconnected, and suffers from a want of correlation 

 with our knowledge of related subjects. There is a 

 need, therefore, for text-books that will set in order the 

 facts now established and point out the lines of develop- 

 ment which our present knowledge is opening up. 



Prof. Greaves has produced a book designed, not 

 primarily for the expert, but to stimulate curiosity and 

 inquiry in the student. The first portion is devoted to 

 general bacteriology, discussing the morphology and 

 schemes for the classification of bacteria, their chemical 

 composition and physiology, and the influence upon 

 them of external conditions such as temperature, heat, 

 disinfectants, and salts. This is a very desirable arrange- 

 ment, especially since the branches of applied bacteri- 

 ology are to-day suffering from the backwardness of our 

 knowledge of the fundamental problems of pure bacteri- 

 ology. One feels, indeed, that the author would have 

 done well to have emphasised more strongly the direc- 

 tions in which such knowledge is most needed. He has 

 also included in this general section such subjects as the 



NO. 2802, VOL. I I 2] 



influence of heat, volatile antiseptics, and arsenic on soil 

 bacterial activities. It would seem more reasonable to 

 deal with these matters in connexion with the soil 

 population, since the facts do not indicate a simple issue 

 between the soil bacteria and the disinfecting agent. 



The middle portion of the book deals with the soil 

 flora and its activities, such as the production of 

 ammonia and nitrate, the fixation of nitrogen, denitri- 

 fication, cellulose decomposition, and the solvent action 

 of bacterial metabolic products on soil minerals. At 

 the conclusion are chapters on the relation of bacteria 

 to water supply, sewage, dairying, food preservation, 

 and various technical processes. 



The completeness with which our present knowledge 

 has been presented, varies very greatly in different parts 

 of the volume. The most interesting part of the work 

 is that which deals with the fixation of atmospheric 

 nitrogen, where the main aspects of the subject are well 

 put forward. Unfortunately, however, reference is 

 omitted to some fundamental work on the soil micro- 

 population without a knowledge of which the student 

 cannot obtain a true picture of the activities of bacteria 

 in the soil. Essential to this, for example, is some 

 knowledge of recent work on the relation between 

 bacterial numbers and the active protozoan fauna in 

 field soil. In criticising Russell and Hutchinson's 

 phagocyte theory of partial sterilisation, the author even 

 states that " the work of Russell and Hutchinson does 

 not consider the probability of the protozoa being in 

 the soil as cysts." The existence of active protozoa in 

 the soil was discovered by Martin and Lewin at Rotham- 

 sted in 191 5, and, in the protozoology department, 

 initiated there to investigate this subject, it has since 

 been shown by Cutler and Crump (1920) that the 

 numbers of active amoebse and flagellates in field soil 

 change from day to day, and that the increase and 

 decrease of certain active amoebse bear an inverse 

 relationship to changes in bacterial numbers. The 

 connexion between active protozoa and bacterial 

 numbers is, therefore, established, with the consequent 

 probability that, if this equiUbrium be upset by some 

 partial sterilisation process, such changes would ensue 

 as were found by Russell and Hutchinson. 



Again, in connexion with the production of ammonia 

 from organic nitrogen compounds in the soil, the author 

 does not emphasise how important is the nature of the 

 energy supply available to the ammonifying organisms, 

 which, apparently, are equally able to derive their 

 energy from a non-nitrogenous source, and, where such 

 compounds are available, may even assimilate ammonia 

 and nitrate, thus causing a temporary loss of these 

 compounds from the soil. The importance of this 

 factor was pointed out by Doryland (1916). In the 

 chapter on the decomposition of cellulose, there is no 



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