838 REPORT— 1897. 



or by adding some gas or other body. This granted, it is not difEcult to see that 

 natural selection will aid in the perpetuation of the symbiosis, and in cases like 

 that of the ginger-beer plant it is extremely difEcult to get the two organisms 

 apart, reminding us of the similar difficulty in the case of the soredia of Lichens. 

 Moreover, experiments show that the question of relative abundance of each 

 constituent aliects the matter. 



1 must now return for a moment to Buchner's discovery that by means of 

 extremely gi'eat pressures a something can be expressed from yeast which at once 

 decomposes sugar into alcohol and carbon-dioxide, and concerning which Dr. Green 

 will inform us more fully. This something is regarded by Buchner as a sort of 

 incomplete protoplasm — a body composed of proteid, and in a structural condition 

 somewhere between that of true soluble enzymes like invertin and complete living 

 protoplasm. 



If this is true, and Buchner's zymase turns out to be a really soluble enzyme, 

 the present theory of alcoholic fermentation will have to be modified, and a 

 reversion made towards Traube's views of 1858, a reversion for which we are in a 

 measure prepared by Miquel's proof in 1890 that Urase, a similar body extracted 

 from the urea-bacteria, is the agent in the fermentation of urea. At present, 

 however, we are not sufficiently assured that the body extracted by Buchner is 

 really soluble, and I am told that very serious difficulties still face us as to what 

 solution is. The enormous pressures required, and the fact that the ' solution ' 

 coagulates as a whole, might suggest that he was dealing with expressed proto- 

 plasm, still alive, but devoid of its cell-wall ; against this, however, must be urged 

 the facts that the ' solution ' can be forced through porcelain and still act, and this 

 even in the presence of chloroform. 



We may fairly expect that the further investigation of Buchner's ' zymase,* 

 Miquel's ' urase,' and the similar body obtained by E. Fischer and Lindner from 

 Monilia Candida will help in deciding the question as to the emulsion theory of 

 protoplasm itself. 



In any case, soluble or not, these enzymes are probably to be regarded as bits 

 off the protoplasm, as it were, and so the essentials of the theory of fermentation 

 remain, the immediate machinery being not that of protoplasm itself, but of some- 

 thing made by or broken otf from it. Enzymes, or similar bodies, are now known 

 to be very common in plants, and the suspicion that fungi do much of their work 

 with their aid is abundantly confirmed. 



Payen and Persoz discovered diastase in malt extract in 1833, and in 1836 

 Schwann discovered peptase in the juices of the animal stomach. Since that time 

 several other enzymes hare been found in both plants and animals, and the 

 methods for extracting them and for estimating their actions have been much 

 improved, a province in which Horace Brown, Green, and Vines have contributed 

 results. 



It seems not improbable that there exists a whole series of these enzymes which 

 have the power of carrying over oxygen to other bodies, and so bringing about 

 oxidations of a peculiar character. These curious bodies were first observed 

 owing to studies on the changes which wine and plant juices undergo when exposed 

 to the action of the oxygen of the air. 



In the case of the wine certain changes in the colour and taste were traced to 

 conditions which involved the assumption that some body, not a living organism, 

 acts as an oxygen-carrier, and the activity of which could be destroyed by heating 

 and antiseptics. It was found that similar changes in colour and taste could be 

 artificialljf produced by the action of ozone, or by passing an electric current 

 through the new wine ; indeed, it is alleged that the ageing of wine can be suc- 

 cessfully imitated by these devices, and is actually a commercial process. 



The browning of cut or broken apples is now shown to be due to the action of 

 a similar oxydase — i.e. an oxygen-carrying ferment, and the same is claimed for 

 the deep-colouring of certain lacks, or lackers, obtained from the juice of plants 

 such as the Anacardiacecs, which are pale and transparent wben fresh drawn, but 

 gradually darken in colour on exposure to air. Bertrand found in these juices an 

 oxydase, which he terms laccase, and which aflfects the oxygen-carrying, and con- 

 verts the pale fluid juice to a hard dark brown varnish. 



