METHODS EMPLOYED IN BACTERIOLOGICAL INVESTIGATIONS. 9g 
different soil conditions. Though it is recognized that the methods 
suggested by different investigators are not adequate for accurate 
quantitative investigations of bacterial functions and conditions in 
various soils, the methods which at this time have been found most 
convenient and suitable for the investigations under discussion are 
briefly reviewed.! 
COUNTS OF BACTERIA. 
Samples of soil were collected with as strict aseptic precautions as 
it is possible to observe under field conditions. Sterile salt-mouth 
bottles were used as containers, and the soil auger used for taking up 
the soil was carefully cleaned and flamed over an alcohol lamp before 
sampling each stratum. In the laboratory 1-gram portions were 
removed from the bottles with a sterile scoop which held the required 
quantity, transferred to 300 cubic centimeters of sterile water in 
500-cubic-centimeter flasks, and the whole shaken thoroughly at short 
intervals for fifteen minutes. One-cubic-centimeter portions of these 
infusions were then removed with sterile pipettes and added to 10 
cubic centimeters of melted beef agar, and plates poured in the ordi- 
nary manner and incubated at 28°C. Counts of bacteria were made 
at the end of five-day periods. 
AMMONIFICATION. 
Sterile peptone solutions having the following composition were 
inoculated with 5 per cent of soil and the ammonia determined at the 
end of seven and fifteen days by distillation with magnesia: 
CPO Css ee eet Pari KA ee see ecet a8 Sa 15 grams 
Dipotassmmyenhospliaketesaor sc he ae Ee? 3 grams. 
Mann esr smiplakes. 52.2225 fei desa ee. 062s ek ee 3 grams. 
Sodicumar ebelorie See paas ha 6 ye oie 1G meshes eo Bs Pe ae) OL EAMS. 
WAG @ Ty ie etee eae rer ci Ih Oe site Crh gids no ye ee oS 1,000 c. € 
1 Lipman, J.G. Experiments on the Transformation and Fixation of Nitrogen by 
Bacteria. Twenty-fourth Annual Report, New Jersey State Agricultural Experiment 
Stations, 1903, pp. 217-285. 
Lipman, J. G., and Brown, Percy E. Methods Concerning Ammonia Formation 
in Soils and Culture Solutions. Report, Soil Chemist and Bacteriologist, New Jersey 
Agricultural College Experiment Station, 1908, pp. 95-105. 
Lipman, J. G.,and Brown, Percy E. Noteson Methods and Culture Media. Report, 
Soil Chemist and Bacteriolégist, New Jersey Agricultural College Experiment Station, 
1908, pp. 129-136. 
Lipman, J. G. Azotobacter Studies. Report, Soil Chemist and Bacteriologist, 
New Jersey Agricultural College Experiment Station, 1908, pp. 187-143. 
Lohnis, F. Ein Beitrag zur Methodik der bakteriologischen Bodenuntersuchung. 
Centralblatt fiir Bakteriologie, Parasitenkunde und Infektionskrankheiten, pt. 2, 
vol. 12, no. 6-8, pp. 262-267, June 24, 1904; no. 11-16, pp. 448-463, July 14, 1904; 
vol. 17, no. 14-16, pp. 518-528, December 7, 1906; vol. 20, no. 24-25, pp. 781-799, 
April 15, 1908; vol. 24, no. 5-7, pp. 183-192, August, 1909. 
Remy, Theodor. Bodenchemische und Bakteriologische Studien. Landwirt- 
schaftliche Jahrbiicher, vol. 35, Supplement 4, pp. 1-62. Berlin, 1906. 
78011°—Bul. 211—11 2 
