RUSSELL AND HUTCHINSON'S PROTOZOAN THEORY 137 



compost soil to 100 C. moist heat for an hour and used a similar 

 series, unheated, as a check. All the flasks received 0.2 per cent, 

 ammonium sulphate some of the flasks received 2 per cent, and 5 

 per cent, ether. In order to obtain vigorous nitrification 170 c.c. 

 of amebne-free extract was inoculated into all the flasks. (This 

 was prepared by leaching 2 kg. of compost soil and 4 liters of sterile 

 water and filtering through filter paper; the microscopic examination 

 revealed the presence of no amebse.) 



"The analyses for nitrate nitrogen were made at the beginning 

 of the experiments and at the end of 100 and 150 days, respectively; 

 the results showed that heating the soil to remove ameba? did not 

 have a beneficial effect upon nitrate formation, contrary to Russell 

 and Hutchinson's work although the addition of a small amount 

 of ether increased nitrification in the flasks containing amebre, and 

 had the opposite effect in the soil free from amebse. This, the 

 authors believe, may be accounted for by the stimulating effect 

 upon the nitrifying bacteria, since the heated soil not treated with 

 ether showed no such increase. 



"Fred concludes (in addition to the above mentioned observa- 

 tions) that ether and carbon bisulphid cause an increased fixation of 

 nitrogen in pure cultures of Azotobacter. The development of deni- 

 trifying organisms is hindered for only a short time, because of 

 treatment with antiseptics. Both Azotobacter and denitrifying 

 organisms are insignificant in a normal soil. Nitrification is at first 

 inhibited and later accelerated by antiseptics, while toxins remain 

 unaffected by treatment. Carbon bisulphid and ether cause an 

 increase in crop yield under sterile conditions. 



"He holds that the increased growth of plants following the use 

 of antiseptics in the soil depends essentially upon the stimulation 

 to the plant itself, in combination with a similar effect on the lower 

 organisms. 



"Fred's work is highly suggestive, but the determination of 

 nitrogen produced is in the form of nitrates alone, and no data are 

 set forth concerning ammonia. That this might affect his results is 

 evident when one takes into consideration the fact that most investi- 

 gators have proved that nitrification is depressed by antiseptics. 



"Furthermore, like many other experimenters he does not con- 

 sider the possibility of protozse cysts passing through the filter 

 paper in the preparation of ' arnebae-f ree extract.' And we have 

 found in our experimental work that cysts do pass through several 

 thicknesses of high-grade filter paper. 



" In much the same manner, Gainey concludes that investigations 

 relative to the effect of toluol and carbon bisulphid upon the micro- 

 flora and fauna of the soil, that: (a) small quantities of carbon 

 bisulphid, toluol, and chloroform, such as have been used practically 

 and experimentally, when applied to soils studies, exert a stimulative 



