133 



each one. The fluid in one of these capsules was then brought to a boil and 1 c. c. 

 from one of the tuhen was added to it and the boiling continued for 1 h minutes. In the 

 same way each of the other tubes was tested. In none oi the 5 capsules was there 

 any reduction of the copper. 



A more conclusive test would })e to grow these organisms in sugar 

 bouillon for some weeks and then determine per cubic centimeter the 

 exact copper-reducing power of the cultures. These should then be 

 heated 10 minutes at 54^^ C. , or thereabouts — i. e. , long enough to destroy 

 the organisms. Thereupon, measured volumes should be pipetted into 

 sterile cane-sugar solutions. To similar solutions should be added equal 

 portions from the cultures after heating them for 10 minutes at 80° or 

 90"^ C. — i. e., long enough to destro}' the supposed invertase. Then 

 after some weeks, if the fluids have remained sterile, their reducing 

 powers should be determined quantitatively. An experiment of this 

 sort was begun with i^y. hyachdld^ but was lost through a contamina- 

 tion which was probably introduced with the thymol. At least the 

 intruding white organisms were capable of growing in the presence of 

 an abundance of this antiseptic at a constant temperature of 50° to 

 52° C. 



As the writer has had no opportunity to repeat the experiment, the 

 question of an invertase must be left an open one. This only is toler- 

 ably certain — none is formed in the absence of cane sugar. 



All of these 4 yellow organisms invert cane sugar readily, as already 

 pointed out. 



Diastase (Amylase). 



The experiments with starchy media, already described, show that 

 the diastasic action of Ph. hyacinthl is very feeble. Nevertheless, 

 some growth occurred, even when the greatest care was taken to 

 exclude all carbohydrate food except pure starch; and as tests with 

 iodine water and with Soxhlet's solution showed that there had been 

 a slight action on the starch, minute quantities of a diastatic ferment 

 must be secreted. The starch which has been acted upon gives the 

 red or amylodextrine reaction with iodine. Ps. stewarti acts on starch 

 slowly, after the manner of Ps. hyacinthi. 



On the contrary, Ps. enmpestris and Ps. j)h(Lseoli destroy starch 

 and amylodextrine promptly in considerable quantities, so that in 

 course of a few weeks none, or very little, is left in the culture tube, 

 even when there were several grams of starch at the outset. 



Experiments with both Pa. campestris and Ps. 2)haseoli showed that 

 starch was converted in the absence of the bacteria (tubes heated for 

 some miiuites at a few degrees above the thei-mal death point and some 

 of the fluid then added to potato starch with antiseptic precautions) 

 and that none was converted if before adding them to the starch the 

 fluids were heated to a point above that at which diastase is destroyed. 



