384 



STATE BOARD OF AGRICULTURE. 



While the actual amounts of phosphoric made soluble as shown in 

 the foregoing tables covering Series I. to VII. are in many cases so 

 small as to be outweighed by the error in chemical determination, there 

 are 3'et innumerable instances in Avhich there is no question as to there 

 being more soluble phos]»horic acid in the inoculated flasks than in the 

 uninoculated. There has been a gradual increase in the phosphoric 

 acid made soluble with each period of chemical examination and this 

 increase in nearly every case has been much greater than would result 

 from mere water solution as shown by the uninoculated controls. In 

 other words the action has been a slow progressive solution. 



At no time during the ex](eriment has there been any indication of an 

 acid reaction in the flasks, which fact seems to ])oint to some force at 

 work other then simj)ly acid as suggested by Koch and Krobcr. 



Satisfied then, from these experiments, that only very small quanti- 

 ties of insoluble phosphate could be made soluble without the in- 

 tervention of an acid, our next step was to study the effect of some of 

 the weaker acids upon bone meal as produced in vitro by bacterial fer- 

 mentations. 



SERIES VIII. 



Lactic acid was the first one selected for our purpose since it could 

 be obtained easily by inoculating sterile milk with a pure cultute of the 

 lactic organism. 250 c. c. of skimmed milk to which 4 grams of bone 

 meal were added gave the basis for the experiment. After sterilization, 

 one set of the flasks was inoculated with a pure culture of B. acidi 

 lactici and the other set kept for sterile controls. At the end of fifteen 

 days, chemical determinations were made yielding the results given in 

 Table No. 11. 25.31% of the bone phosphate was rendered soluble in 

 15 days by the lactic acid present in the sour milk. 



Table No. 11. Solvent Action of the Lactic Acid from Sour Milk. 



Nutrient Solution: 



250 c c. Milk -t- 4 grams bone meal. 



Culture used for the Inoculation. 



m. g -P 2O 5 in 250 c. c. of the solution after 15 days 



Sterile 

 Control. 



318.8 



B. acidi 

 lactici. 



557.0 



Duration of 

 Experiment 15 days. 



m. g. P oO 5 in 250 c. c. of the solution made soluble 

 by the bacteria after 15 days 



258.2 



Per cent of P jO s made soluble by the bacteria . 



25.31 



