308 STATE BOARD OF AGRICULTURE. 



Investigations liave been conducted along- similar lines in this labora- 

 tory for the past two years, during- which time more than five hun- 

 di-ed different determinations have been made. Our purpose from the be- 

 ginning has l>een to demonstrate quantitatively. iC possible, that the Iri- 

 calcium phosphate of raw bone meal and the insoluble phosphate of 

 natural raw rock phosphate are made soluble by soil bacteria rather ilmn 

 to attempt any explanation of the processes involved. 



PRELIMIXARY DISCUSSION. 



Knowing that the composition of a bacterial medium (1) influences 

 the physiological activities of the organisms gi'ow^n in it, the first prob- 

 lem to confront us Mas, naturally, the kind of a medium to employ to 

 secure the optimum results. This was met by taking several media dif- 

 fering principally in tlie form and amount of the nitrogen they con- 

 tained. 



The exact comjiosition of each solution is given under the discussion of 

 its particular series. To 4 grams of bone meal prepared as herein de- 

 scribed, placed in a 1,000 c. <•. Florence flask, 250 c. c. of the bacterial 

 liquid was added. These flasks were then sterilized in flowing steam 

 for one hour on three successive days. The usual sterilization for 

 twenty to thirty minutes by the discontinuous method was found to 

 be unsatisfactory, owing to the presence of a very resistant spore-forming 

 organism found in the bone. 



After the third sterilization, all the flasks of a series were inoculated 

 in triplicate from twenty- four hour agar streak cultures and placed in 

 a constant temperature room at 23° C. to 25° C. All of the flasks were 

 thoroughly shaken once a week during the whole period of experimenta- 

 tion. P'ach series contained 33 flasks, three of each culture and three 

 uninoculated controls. Each series, unless otherwise stated, was ex- 

 amined quantitatively for soluble phosphoric acid after 30. 60 and 90 

 days. 



Where the phosphate rock was used in place t)f the bone, 4.5 gra,ms 

 were taken for each flask, this amount being efjuivalent in phosphoric 

 acid to that contained in 4 gTams of bone. 



BACTERIAL CULTURES. 



The bacterial cultures used in our work Avere partly laboratory stock 

 cultures and partly those isolated fi'om agar plates nmde from a water 

 suspension of garden soil. To the latter cultures have been assigned the 

 laboratory numbers 1, 3, 4 (Ij. ramosus), 7, S. The stock cultures were 

 J{. subtilis. 1». mycoides, B. proleus vulgaris and 1>. coli communis. 



BOXE MEAL. 



The bone meal which furnished the tri-calcium phosphate was obtained 

 from Swift & Co., Chicago, Ills., and was known as Medium l^ure Raw 

 P»one Meal. It contained: — 



25.5% Total r,0, 

 3.05% Nitrogen 

 1.9% Fat 



(1) See page 27. 



