Royal Society. 475 



the author next proposed to himself to inquire, by what means this 

 action is either destroyed, retarded, or promoted, and whether any 

 means exist of so modifying the action as to lead to the formation of 

 particular substances in preference to others. From a variety of 

 experiments undertaken with this object, he draws the following; 

 conclusions : — 



1 . There exist no means short of the complete destruction of the 

 ferment, capable of arresting its action on rubian, except exposing it 

 while in a moist state to the temperature of boiling water. Even 

 when exposed to that temperature, after having been previously 

 dried, its fermenting power is not entirely lost, but merely weak- 

 ened. ^ 



2. By the addition of various substances, usually classed as 

 antiseptic, such as sulphuric acid, arsenious acid, sugar of lead cor- 

 rosive sublimate, alcohol, and oil of turpentine, during the process of 

 fermentation, the action of the ferment is not destroyed ; it is merely 

 retarded and modified. 



3. The more the action of the ferment on rubian is retarded, the 

 more rubiretine and verantine, and the less alizarine are formed ; so 

 much so, that in some cases the alizarine disajipears entirely from 

 among the products of decomposition, which then consist almost 

 solely of rubiretine and verantine. The formation of rubiafine and 

 rubiagine is promoted when the action of the ferment is moderately 

 retarded, but diminishes again or entirely ceases when the retarda- 

 tion is very great. Of the two the rubiagine is the first to disappear 

 when any retardation takes place. 



4. By the addition of small quantities of alkalies during the i)ro- 

 cess of fermentation, the action is, as regards its duration, if not 

 promoted, at all events not retarded ; and as regards the relative 

 quantities of the various substances produced, the amount of alizarine 

 is thereby decidedly increased, while that of the rubiretine and 

 verantine is diminished. 



Most of the ordinary fermentative substances, such as albumen 

 caseine, gelatine, and yeast, are incapable of effecting the decompo- 

 sition of rubian, even when mixtures of these various substances 

 with watery solutions of rubian are allowed to stand until they enter 

 into a state of putrefaction. Emulsine is the only substance capa- 

 ble of forming an effective substitute for erythrozym. Its action is 

 similar to that of the latter substance ; it gives rise however to the 

 formation of a much larger proportional quantity of alizarine. The 

 action of the peculiar albuminous substance, discovered by Braconnot 

 in the root of the HeliantJius (uberostis, on rubian, was also examined 

 It exerts only a slight effect on the latter, the only products of de- 

 composition formed being rubiretine and verantine. 



Tlie author considers the fact of erythrozym being almost the only 

 ferment which is capable of effecting in any considerable degree the 

 decomi)Osition of rubian, as tlie best proof of its being a pecu- 

 liar and distinct substance. When i)rej)ared by precii)itatioii with 

 alcohol, erythrozym is obtained as a chocolate-coloured granular 

 mass. When dried it coheres into hard lumps, which are almost 



