162 NINTH REPORT. 



into the second set, the synthetic medium phis 4% of saccharose; into 

 the third, fourth and fifth sets was poured the synthetic medium phis 1%, 

 2%, and 4% dextrose respectively. Not a germ was found which gave any 

 visible action in the plates containing no sugar; but in the presence of the 

 4% saccharose, the 1%, the 2% ancl the 4% dextrose, some of the germs 

 gave a marked action, upon the calcium .carbonate and the dicalcium and 

 tricalcium phosphates. Some even dissolved those suspended particles 

 which were, in cases, an inch from the growth of the germ. As before, no 

 definite action could be noticed upon the bone or the rock phosphates. 

 The solvent action of some germs seems to be greater in the presence of the 

 larger percentage of sugar, while that of others seems to be as great with 

 1% as with 4%. Now, if we use meat infusion- — a Titer of water to a pound 

 of beef — instead of the water in the synthetic medium, we find that the 

 solvent action exerted by bacteria is not nearly so great. 



In order to get the cultural conditions more nearly like those existing 

 in the soil, we used a medium composed of soil leachings with 2% agar. No 

 solvent action could be noticed. But when sugar was added to this medium 

 the action is about as marked as that with the synthetic medium described 

 above. 



It might be interesting to note here that according to our experiments 

 those germs which, in the presence of sugar, are the most active acid pro- 

 ducers are also the germs which, in the presence of albuminoids and the ab- 

 sence of sugar, are the most active alkali producers. And again that these 

 active germs are the ones which have shown the greater solvent action. In 

 no case has there been any visible action shown by a germ which is feeble 

 in changing the reaction of a medium. Twelve out of twenty- five 

 bacteria isolated from the soil were found to give a definite, visible solvent 

 action. One which, produces no gas but a larger amount of acid from 

 sugars than ai\y of the others, shows the greatest action upon the calcium 

 carbonate, while other germs which produce gas — largely carbon dioxide — 

 but not as much acid as the former, give an action more marked than that 

 of the stronger acid producer upon the dicalcium and tricalcium phosphates. 

 These points, with others noticed during the experiments, have led us to 

 believe that, while acid is a great factor in dissolving insoluble phosphates, 

 the carbon dioxide liberated from carbohydrates by the gas producing bac- 

 teria must not be overlooked as a solvent agent. 



"£5^ 



Agricultural College, Mich. 



