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Messrs. F. L. Usher and J. H. Priestley. [Apr. 30, 



colour when immersed in a solution of rosaniline decolourised with sulphurous 

 acid. The experiment was repeated several times with the same result, 

 and when performed on a larger scale the distillate from an aqueous 

 solution of the gelatine was found to contain formaldehyde, the substance 

 being identified by the characteristic methyleneaniline and tetrabromo- 

 hexamethylenetetramine reactions. The melting point of the methylene- 

 aniline was within 2° of that of the pure substance. It will be 

 seen that the action which takes place under these conditions is the same 

 as that which occurs in a green plant when the protoplasm has been killed 

 and the enzymes destroyed ; the accumulation of formaldehyde is possible 

 so long as any chlorophyll remains to remove the hydrogen peroxide. The 

 use of gelatine may be avoided by a modification of the arrangement just 

 described. A layer of water in a shallow porcelain dish replaces the 

 gelatine, and the chlorophyll film is obtained by dropping the petroleum 

 ether solution over the surface from a pipette, at the same time directing 

 a current of air against it so as to evaporate all the solvent before the 

 chlorophyll can collect in patches. Experiments performed in this manner 

 gave the same results as those with the gelatine films. The ]atter are more 

 convenient to manipulate, but it is preferable to dispense with the gelatine 

 if the object is to collect as much formaldehyde as possible, since this 

 substance has a larger concentration in the residue than in the distillate. 



A second series of experiments was undertaken with the object of 

 ascertaining whether the process could be carried as far as the evolution 

 of gaseous oxygen. It has already been pointed out in a previous paper 

 that the decomposition of the hydrogen peroxide in the plant is brought 

 about by an enzyme, probably a " catalase," and it was also shown that a 

 certain amount of oxygen can be evolved from plants which have been 

 killed, provided that the enzymes are not destroyed. 



The catalase employed was obtained from sheep's liver by extracting the 

 dried and powdered material with water containing a little thymol, the 

 enzyme being precipitated by excess of absolute alcohol. The arrangement 

 of the experiments was the same as in the first series, but the gelatine was 

 made up with an aqueous solution of the catalase instead of with pure water, 

 and the solution thus prepared was spread upon a strip of tinned iron 60 cm. 

 long and 3 cm. wide. After painting it over with chlorophyll solution, the 

 strip was placed inside a glass tube, sealed at one end, just large enough to 

 contain it, and which was afterwards drawn out at the open end to a capillary, 

 and sealed to a T- piece connecting it, through two stop-cocks, with a supply 

 of carbon dioxide, and a pump. The carbon dioxide used was passed over 

 red-hot copper in order to remove traces of oxygen, and the tube was 



