EXPERIMENT STATION BULLETINS. 



363 



the first stage of development, only the final products have been 

 considered as important. This is natural from the commercial stand- 

 point of the brewer, distiller, and butter-maker, but the scientist who aims 

 at a complete understanding of the physiological process has to consider 

 all phases of the growing cultures. 



An illustration for this fact can be given in the results obtained by 

 the Remy method for testing soils. It consists in inoculating a sterile 

 peptone solution with a certain amount of soil and determining the 

 amount of ammonia produced after a certain number of days. Besides 

 ammonia production, other soil properties, like nitrification, nitrogen 

 fixation, etc., are tested in corresponding solutions. The ammonia is 

 iisually determined just once, after 3 to 8 days, under the supposition 

 that after this time it does not increase. This is not always true, as 

 can be seen easily from the data obtained with three Michigan soils, a 

 muck, a sandy loam, and a vei'y poor sand. The ammonia produced by 

 10 grams of soil in 100 cc. of a 1% peptone solution at 20°C. gave the 

 following data: 



AaUMONIA PRODUCTION IN 100 CC. OF PEPTONE SOLUTION BY 10 GRAMS OF SOIL. 



(mg. nitrogen in form of ammonia per 100 cc). 



Days. 



Muck { 



Loam I 



Sand 



23 



110.6 

 113.1 



114.5 



102.8 

 107.7 



The table shows veiy plainly that one single determination of ammonia 

 cannot j)ossibly give a correct idea of the changes brought forth by the 

 soils. After two days, the muck soil has produced about nine times as 

 much ammonia as the sand, and the loam about five times as much. This 

 jiropoiiion, 1:5:9 is entirely changed after four da3\s; it is 1:8:8, muck 

 and loam being alike. After six days, the loam is ahead, but the sand 

 also begins to ammonify more rapidly; the relative amounts of am- 

 monia are now 1:3:2.6. From the eighth da}^, muck and loam are very 

 much alike, while the sand is coming up more and more, though not 

 entirely reaching the other two soils; the final proportion is 1:1.1:1.1. 

 These proportions show better than long discussions that the Remy 

 method in its present form cannot give an understanding of the bacter- 

 iological properties of a soil. What time would be the most adequate 

 for the distillation? At first, the muck is high, then the loam is high, 

 and at the end, all three soils are very much alike. Even if all bacteri- 

 ologists would agree to keep all cultures at the same temperature for 

 the same length of time, the simple analysis of one culture after seven 

 days would not give a definite knowledge of the previous and the follow- 

 ing changes. The peculiar difference between loam and muck soil could 



