1878.] 



the Influence of Light upon Protoplasm. 



205 



carbonic oxide, or an oxidation resulting in water and carbonic acid 

 alone. 



We found that whether oxygen was removed by exhaustion at the 

 Sprengel pump, or by boiling the solution and inverting in mercury 

 without access of air, decomposition was alike prevented. It was evi- 

 dent, therefore, that oxygen was the agent of destruction under the 

 influence of sunlight, for of course the nitrogen of the air may be put 

 out of the question. 



We' next experimented on a representative of a most interesting 

 class of bodies, which in the complexity of their composition probably 

 approach protoplasm itself. We refer to the so-called soluble or indi- 

 rect ferments, of which we selected zymase, the soluble ferment of. 

 yeast, as a type. 



We noticed last year that sunlight had no retarding effect on the 

 action of this class of ferments, but we did not then investigate the 

 effect of prolonged insolation on the ferment itself. Accordingly, on 

 June 25th, some water in which a fragment of yeast had been macerated 

 was thrice passed through double layers of the finest filtering paper. 

 Examined under the microscope, the liquid, which was quite clear, was 

 found to contain no trace of Torula. Salt was then added to satura- 

 tion, in order to avoid putrefaction, and the solution was divided 

 between two series of test-tubes, one series being insolated, and the 

 other incased in the usual way. 



On July 19th about three drachms of freshly made syrup was placed 

 in each of a number of cprouvettes. These were divided into two sets ; 

 to one set was added five grain- measures of the insolated zymase solu- 

 tion, and to the other a corresponding quantity from the incased tubes ; 

 a watch-glass was placed over each, and they were left for some hours. 

 At the end of this time, five grain-measures of the syrup to which 

 zymase from the incased tubes had been added completely reduced an 

 equal quantity of a Fehling's solution, while no perceptible change 

 was caused by the syrup which had been treated with insolated zymase. 



It is clear, therefore, that sunlight destroys the specific power of this 

 ferment for hydrating cane-sugar. 



We next experimented on zymase in vacuo. On August 16th a solu- 

 tion of the ferment, prepared in the same way as before, was divided 

 between eight tubes, two of which were insolated and two incased. 

 The remaining four were simultaneously* exhausted at the Sprengel 

 pump and sealed. The contents gave a sharp "water-hammer" click, 

 bearing testimony to the excellence of the vacuum. Two of these 

 tubes were insolated and two incased. 



On September 5th, eight eprouvettes of fresh syrup were inoculated 

 with liquid from each tube as before, and allowed to stand overnight, a 



* See Appendix. 



