478 



STATE BOARD OF AGRICULTURE. 



TABLE Xir. 



Endpoint and adsorption. — The tables X-XII show one rather inter- 

 esting point, namely Ihe ammonia in the saturated sands. This seems 

 rather strange since the conditions in the saturated sand are "more 

 strictly anaerobic than in solution. The sand is a mechanical ob- 

 stacle to the diffusion of oxygen into the deeper layers, and prevents 

 also the currents Avhich help to distribute oxygen through li(piids. The 

 explanation through air held mechanically by the sand does not hold 

 true because exactly the same is Irue with Bactcriuni lactis acidi (see 

 Tables XIX-XXU). These would be retarded by the })resence of oxygen, 

 but they develop better in sand saturated wilh milk than in milk alone. 



These data have a certain similarity with the finding of plant physiolo- 

 gists, that the toxic action of certain poisons is reduced or even disap- 

 pears entirely through the addition of such finely divided materials as 

 quartz sand, filter pa]>er or paraffin. The explanation given is gener- 

 ally adsorption, though in no case the decrease of poison in the solu- 

 tion has been proved by analysis. 



Gibbs determined with a few minerals salts the amounts actually 

 adsorbed by quartz sand, and found it in some cases to be unmeasurable, 

 in others to be less than 1 mg per square meter of surface. This 

 speaks very plainly against any explanation of the high ammonia yields 

 in the well-aerated soils while it might suffice for the difference in 

 solution and water-logged sand. 



Endpmnt and Ammonia Concentration. — All these experiments make 

 it seem rather doubtful whether the growth of B. mycoides is actually 

 limited by the accumulation of ammonia or rather ammonium carbonate. 

 If this were the case, one would have to concludi* necessarily that in 

 sand the bacteria can tolerate 8 times as much ammonia as in solution. 

 The tolerance for ammonium carbonate can be easily tested. A stand- 

 ard Sdlutioii of ammoTiinm carbonale was pasteurized at 80'^C. for half 

 an hour, and was then mixed with a sterile peptone solution in certain 

 proportions. After reix?ated inoculation, B. mycoides was found to 

 grow in the presence of 200 mg NH^ per 100 cc. If, therefore, the de- 

 composition of i>eptone solution ceases at 2.3 mg NTT. per 100 cc. this 

 is not due to the accumulation of ammonia. 



Endpoint and Oxidation. — The jirevious exi)eriments establish the facts 

 that the ammonia formation by B. mycoides is not com|)arable to the 

 acid or alcohol forniation by other inicroiirganisms. The neutraliza- 

 tion of acid, the removal of alcohol allow a new development of the 

 organisnis, consequently they are inhibiting ])roducts. The ammonia 



