34 Dr. A. J. Ewart. Supposed Eatracellular [Oct. 11, 
not aware of its existence, for Loew discusses the properties, forms, and 
distribution of his catalase very fully. 
The Evolution of Oxygen. 
By smearing gelatine chlorophyll films with a catalase enzyme, Usher 
and Priestley obtained an evolution of oxygen in the presence of carbon 
dioxide and light. I have not been able to obtain any satisfactory 
proof of this fact, and must point out that gelatine films smeared over 
with an oily film retain oxygen for some time and only give it off slowly 
in an atmosphere of nitrogen. After covering with chlorophyll and 
a catalase juice from Vadllisneria, the films were kept in an atmosphere of 
nitrogen over mercury, a little carbon dioxide added and, after exposure to 
light, the gas was analysed in a Bonnier-Mangin apparatus. Barely 
measurable traces of oxygen were present in some cases, but hardly more 
than can be explained on the above assumption, and the amount of carbon 
dioxide underwent no appreciable diminution, but if anything a slght 
increase. Further, if the films were kept over night in an atmosphere of 
nitrogen in the presence of a piece of pyrogallol-potash paper subsequently 
drawn out by a thread, on adding carbon dioxide next day and exposing to 
hght no trace of oxygen was found, although the films at the commencement 
of the exposure appeared to be green and normal. Apparently, therefore, 
the decomposition of chlorophyll on exposure to light and the resultant 
production of aldehyde is not accompanied by any appreciable evolution of 
free oxygen. Further, no hydroxyl could be detected in any of the films by 
testing with coloured cell sap and cyanin. Nor was the pink coloration 
produced on testing the films with decolorised magenta lessened by boiling 
the gelatine previously to testing, which should have been the case had any 
hydroxyl been present. 
Dead cells of Hlodea and Vallisneria were also tested by the bacterium 
methods for an evolution of oxygen, but without effect, using pure aerobic 
forms. If the green cells had been exposed to strong light for some hours 
until bleached and were then tested, it was found that the bacteria ceased to 
move or only moved very slowly in their immediate neighbourhood, even 
when the surrounding medium was fully supplied with oxygen. After the 
leaves had been boiled in dilute hydroxyl and soaked in cold water for a day, 
they showed the usual chemotropic attraction to aerobic bacteria in the 
presence of oxygen, due to the exudation of chemotropic substances. It is 
evident, therefore, that the aldehyde produced by the decomposition of the 
chlorophyll is able to prevent the detection of the presence of oxygen by the 
bacterium method, a danger which has not previously occurred to myself or 
