272 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



A Technic for the Bacteriological Examination 



OF Soils. 



H. A. NoYES* AND Edwin VoiGx.f 



For nearly half a century investigators have been developing bacteriologi- 

 cal technic. Most of the "standard" methods that have resulted from past 

 investigations are adapted to medical rather than to industrial bacteriology. 

 The results obtained by following the average technic are onlj^ "qualitatively 

 quantitative" for the methods used are qualitative. 



Only of late has extended research been done in the field of soil bacteriology 

 and consequently there is no standard technic for the bacteriological examina- 

 tion of soils. Judging from recent publications soil bacteriologists are adapt- 

 ing medical methods with varying successes and failures. Of late (1) a move 

 has been made to standardize methods for the bacteriological examination 

 of soils. Methods that are accepted as "standard" will have to be founded 

 on the fundamental principles of physics and chemistry. Soil physics is not 

 completely understood and the fundamental chemical changes going on in 

 the soil have not been worked out so advances in bacteriological methods will 

 of necessity have to be related to the development of soil physics and soil 

 chemistry. The following article is submitted with the hope that it may 

 bring out some applications of physical and chemical technic worthy of con- 

 sideration by other investigators and may help a little in tlie standardization 

 of methods of technic. These methods have been successfully follow(>(l in 

 the Ilorticullural Research (^heiuistry and Bacteriology laboratories of the 

 Purdue Agricultural Experiment Station during the past three years. Tlie 

 technic followed, while not entirely original with the authors of this paper, 

 has greatly facilitated the manipulation of sample, media, and apparatus, 

 without in any way impairing tlio accuracy of the methods used. 



That part of the apparatus which differs from that used in most la])()ra- 

 tories is described below. 



S.VMPLER FOR TaKING SoIL SaMPLE. 



For sampling the soil, the bacteriologist's soil sampler is u.sed. Tlii.b 

 sampler is the result of an attempt on the part of the senior author to devise 

 a piece of apparatus that would overcome the inaccuracies that occur through 

 the employment of the usual methods of sampling. The authors have con- 

 siderable data which show that differences in the aeration ot soils affect the 

 bacterial content and are hence stronger advocates than before, for the 

 sampler. We quote as follows from tlie published article which deals with 

 the bacteriologist's soil samj)ler.'- "The sampler is a brass tube 11 inches 



♦Research assistant in Horticultural Cliuiuisiry and Bacteriology. 

 tResearch studoiU. 



