November 8, 1912] 



SCIENCE 



611 



Not only are standardization of methods 

 and interpretation of results, as well as a 

 stiU further recognition of the efEeet of 

 various groups of bacteria, one upon the 

 other, much to be desired; but an appre- 

 ciation of the fact that something else than 

 the bacteria go to make up the microscop- 

 ical life of the soil, must be more generally 

 taken into consideration, in our attempts 

 to find out what actually goes on in the 

 ground. It must be confessed that thus 

 far any knowledge of the algal, fungal or 

 protozoal inhabitants of the soil has tended 

 to confuse rather than clarify any conclu- 

 sions regarding the phenomena induced by 

 a single group of organisms. 



Perhaps no better example of the cha- 

 otic conditions of the present status of the 

 microbiology of the soil can be cited than 

 in the recent revival of a consideration of 

 the effect of heat and various so-called 

 antiseptics on crop production, and the 

 supposed relations of protozoa to the 

 problem. That the addition to soil of car- 

 bon bisulphide, toluol, ether and similar 

 agents, will under certain conditions bene- 

 fit some crops, has of course been known 

 for nearly twenty years, and as early as 

 1888 Frank believed that sterilizing soil 

 with steam increased the solubility, or 

 availability, of mineral and organic sub- 

 stances. 



Various theories, from the mere removal 

 of superabundant, though harmless, bac- 

 teria, to the destruction of toxins, have 

 been proposed to account for this beneficial 

 effect, but it remained for Russell and 

 Hutchinson, of the Rothamsted Station, to 

 stimulate interest in the subject. These 

 investigators, in October, 1909, announced 

 that they had found the increased pro- 

 ductiveness of partially sterilized soil to be 

 due to an excess of ammonia, arising as a 

 result of the bacterial decomposition of 

 soil substances, these bacteria being able 



to multiply enormously on account of the 

 removal, by heat or volatile substances, of 

 large protozoa which normally feed upon 

 the bacteria. This announcement was 

 hailed both in this country and abroad as 

 the greatest discovery pertaining to the 

 soil, since Hellriegel 's interpretation of the 

 beneficial effect of bacteria in the root- 

 nodules of legumes! 



A student in my laboratory becoming 

 interested in the problem, undertook a con- 

 siderable number of preliminary experi- 

 ments, the results of which seemed to war- 

 rant a more elaborate investigation into the 

 effect of soil sterilization upon crop pro- 

 duction. It is not necessary to go into 

 details at this time, but laboratory, green- 

 house and field tests all indicated most 

 decidedly that the theory of Russell and 

 Hutchinson is not of universal application, 

 and the importance of the protozoa, so far 

 as their effect upon bacteria is concerned, 

 has been overestimated. It is true that 

 Russell and Hutchinson themselves consid- 

 ered the removal of the protozoa as being 

 but one factor concerned in the benefits 

 accruing to plants, by the use of antisep- 

 tics, and it may be that the prominence 

 given to this aspect of their work is due to 

 the advertising propensities of those not 

 immediately concerned with the investiga- 

 tions. This is unfortunately sometimes the 

 case. The fact remains, however, that in 

 many of the comments published by those 

 rather closely associated with Russell and 

 Hutchinson, the effect of antiseptics upon 

 protozoa is deemed to be the only one worth 

 considering, and to which all resulting 

 benefit is due. 



Within the last few months, several 

 papers have appeared which likewise fail to 

 agree with Russell's and Hutchinson's re- 

 sults. Goodey, publishing in the Proceed- 

 ings of the Boyal Society, shows that at least 

 one important group of protozoa, micro- 



