McKenney On Luminous Bacteria. 217 



the bacteria were subject to the action of the acid before its neutraliza 

 tion. Immediately the media became acid, i. e., the moment all the 

 bacteria were subjected to the action of the acid, the light instantly dis 

 appeared. 



Numerous experiments with nitric, sulphuric, orthophosphoric, formic, 

 acetic, lactic, succinic, malic, tartaric, oxalic and citric acids, gave re 

 sults essentially the same as those obtained with hydrochloric acid. At 

 the moment the media turned just weakly acid, the light emission at 

 once ceased. Naturally, in proportion as the normal acid was weak, or 

 the acid dilute, so was the actual quantity of acid solution required to 

 give an acid reaction to the medium and destroy light, the larger. The 

 end result of a dark culture and slightly acid reaction of the medium 

 was the same in all cases. 



A few experiments were made to learn the effect of the acid salts. 

 The dihydric phosphates of sodium and potassium NaH^PO ? and 

 KH;jPO T were employed for this purpose. Quite large quantities of 

 the solutions of these salts were needed to render the culture media acid. 

 In each case, however, as soon as the medium became slightly acid, the 

 culture became at once dark. 



In cultures thus treated with acids the light never returned. In 

 most cases, even when the culture was made weakly alkaline within five 

 minutes of the acid treatment, light did not again appear in the culture. 

 In cultures which had been made alkaline after acidification with the 

 acid phosphates, light was again emitted within 12 hours of the addition 

 of the alkali. 



A few experiments to learn the effect of excess of Na OH and KOH in the 

 media were also tried. Growth only occurs in media which turns red 

 litmus light blue. If 2 to 4 drops of decinormal KOH or NaOH be 

 added to a good luminous bouillon culture light production ceases in 

 stantly, and subsequent reduction of excessive alkalinity never permits 

 any return of light. Inoculations made from such cultures do not take, 

 showing the bacteria to have been killed and not simply rendered in 

 active, as is the case when light is destroyed by acids. 



The experiments here recorded for Bacterium phosphorescens were re 

 peated with Bacillus phosphorescens and Microspira luminosa. Like re 

 sults were obtained with both. 



It may be well to briefly note here the methods employed for the in 

 troduction of reagents into the cultures. In the preliminary experi 

 ments the cotton plug was removed, the quantity of sterile reagent 

 quickly introduced with a pipette and the cotton plug at once replaced. 

 Although experience showed that there was rarely any bacterial con 

 tamination by this method, still there was the danger. Since the cul 

 tures were kept under observation for some days after treatment, a 

 method of experimentation was devised which entirely precludes bacter 

 ial contamination during the course of the experiment. 



Small glass tubes were taken, drawn out to form small capillary tubes 

 and on one end of such a tube a very thin-walled bulb was blown. Care 

 was taken to have the walls of the tube heavier than the bulb wall. A 

 measured quantity of the desired reagent was introduced into the bulb 



