TRANSACTTONS OP THE SECTIONS. 65 



constitution and physiological action. It has long been Imown that the ferro- 

 cyanide of {potassium does not act as a poison on the animal system, and Bunsen 

 has shown that the kakodylic acid, an arsenical compound, is also inert. Crum 

 Brown and Eraser find that the methyl compounds of strychnia, brucia, and thebaia 

 are much less active poisons than the alkaloids themselves, and the character of 

 their physiological action is also different. The hypnotic action of the sulphate 

 of methyl-morphium is less than that of morphia ; but a reverse result occui's in the 

 case of atropia, whose methyl and ethyl derivatives are much more poisonous than 

 the salts of atropia itself. 



Before proceeding to the subject of fermentation, I may refer to Apjohn's 

 chemico-optical method of separating cane-sugar, inverted sugar, and grape-sugar 

 from one another when present in the same solution, by obser\ing the rotative 

 power of the syrup before and after inversion, and combining the indications of 

 the saccharometer with the results of an analysis of the same S3'rup after inversion. 

 Heisch's test for sewage in ordinary water is also deserving of'notice. It consists 

 in adding a few grains of pure sugar to the water, and exposing it fi-eely to light 

 for some hom-s, when the liquid will become turbid from the formation of a well- 

 marked frmgus if sewage to the smallest amount be present. Frankland has made 

 the important observation that the development of this fungus depends upon the 

 presence of the phosphate, and that if this condition be secured, the fungus will 

 appear even in the pm-est water. 



The nature of fermentation, and in particular of the alcoholic fennentation, haa 

 been lately discussed by Liebigwith consummate ability, and his elaborate memoir 

 will well repaj'- a careful perusal. Dr. Williamson has also given a most instructive 

 account of the subject, particularly with reference to the researches of Pasteur, in 

 his recent Cantor lectures. A brief statement of the present position of the 

 question will therefore not be out of place here. It is now thirty-four years since 

 Cao;niard de La Tour and Schwann proved by independent observations that yeast- 

 globules are organized bodies capable of reproduction by gemmation ; and also 

 inferred as highly probable that the phenomena of fermentation are induced by the 

 development or living action of these globules. These views, after having fallen 

 into abeyance, were revived and extended a few years ago by Pasteur, whose able 

 researches are familiar to every chemist. Pasteur, while acknowledging that he 

 was ignorant of the nature of the chemical act, or of the intimate cause of the 

 splitting up of sugar in the alcoholic fermentation, maintained that all fermenta- 

 tionsproperly so called are coiTelative with physiological phenomena. Accordino- 

 to Liebig, the development and multiplication of the yeast-plant or fungus is 

 dependent upon the presence and absorption of nutriment, which becomes part of 

 the living organism, while in the process of fermentation an external action takes 

 place upon the substance, and causes it to split up into products which cannot be 

 made use of by the plant. The vital process and the chemical action, he asserts, 

 are two phenomena which in the explanation must be kept separate from one 

 another. The action of a ferment upon a fermentable body he compares to the 

 action of heat upon organic molecules, both of which cause a movement in the 

 internal an-augement of the atoms. The phenomena of fermentation Liebio- refers 

 now, as formerly, to a chemico-physical cause, — the action, namely, which a sub- 

 stance in a state of molecular movement exercises upon another of highly complex 

 constitution, whose elements are held together by a feeble affinity, and are to some 

 extent in a state of tension or strain. Baeyer, who considers that in the alcoholic 

 and lactic fermentations one part of the compound is reduced and another oxidized, 

 adopts the view of Liebig, that the molecules of sugar which undergo fermentation 

 do not serve for the nourishment of the yeast-plant, but receive an impulse from it. 

 All are, however, agreed that fermentation is arrested by the death of the plant ; 

 and even a tendency to the acetous fermentation in wine may be cliecked, as 

 Pasteur has shown, by heating the wine to a temperature a little below the boiling- 

 point in the vessel in which it is afterwards to be kept. 



I regret that the limits of an address like the present forbid me to pursue 



further this analysis of chemical work. Had they admitted of abridgment, 



I should gladly have described the elaborate experiments of Gore on hydrofluoric 



acid and the fluoride of silver. The important researches of Abel on explosive 



1871. 5 



