1878.] the Influence of Light upon Protoplasm. 



203 



Pasteur solution, previously boiled ; one end of each was then sealed. 

 They were then placed in a water-bath, with the unsealed end project- 

 ing above the water, and after prolonged and repeated boiling this 

 end also was sealed. The sealed bulbs were then thoroughly washed 

 with distilled water, to remove all traces of Pasteur solution from their 

 external surfaces, and were each finally sealed up in a tube (fig. 2) 

 containing distilled water in such proportion that, when the bulbs 

 were subsequently broken, the mixture produced a fluid of the ordi- 

 nary strength. Four were incased in laminated lead and five in- 

 solated. 



To prove that the water employed was capable of setting up 

 bacterial or other development, a number of tubes containing Pasteur 

 solution sterilised by repeated boiling and plugged with cotton wool 

 were divided into two series ; to each tube of the one set a few drops 

 of the water were added with a superheated pipette ; to the second 

 series no water was added, but, in order to place them under the same 

 conditions, the superheated pipette was successively dipped into each. 

 All of the series inoculated with water speedily teemed with Bacteria ; 

 the second series remained clear. 



The experiment commenced on April 3rd. About the end of May, 

 the bulb in one of the insolated tubes was accidentally broken, so that 

 the concentrated Pasteur solution of the bulb mingled with the dis- 

 tilled water of the tube. In a few days the mixture became turbid 

 with Bacteria and Torula. We shall again refer to the behaviour of 

 this tube. 



The remaining bulbs were broken towards the close of July by 

 jerking them against the ends of the tubes. The result was that, with 

 one exception, the mixture in the tubes which had been insolated has 

 remained clear to the date of writing (September 1st), but in each 

 instance the incased tubes became turbid with organisms. 



In the single insolated tube which broke down nothing could be 

 seen on careful examination with yV' but round- celled Torula ; there 

 was a complete absence of all bacterioid life. The incased tubes all 

 contained Torula, Bacilli, Bacteria, in active movement, and, in two 

 instances, a number of short, squarish, highly refractive particles. 



It is evident, therefore, that light is injurious to " germs,"' even 

 when contained in ordinary distilled water. There is, however, an 

 important fact in connexion with this which must not pass unnoticed. 

 We have described how a tube in which the bulb had accidentally been 

 broken after exposure to sunlight for six or seven weeks, in April and 

 May, speedily teemed with Bacteria. It happens that, during portions 

 of this time, we had insolated tubes, containing ordinary Pasteur 

 solution, with the result that all bacterial development was prevented 

 by a few days' exposure to the sun, and organisms, if they appeared 

 after the tubes had been incased, were torulaceous or mycelial. There 



