Part 1 (1/2)

YEAST

By Thoht the particular subject of Yeast for two reasons--or, rather, I should say for three In the first place, because it is one of the simplest and the most familiar objects hich we are acquainted In the second place, because the facts and phenomena which I have to describe are so simple that it is possible to put therams which are needed when matters are more complicated, and which, if I had to refer to the away froelymyself heard And thirdly, I have chosen this subject because I know of no fae and experience, the examination of which, with a little care, tends to open up such very considerable issues as does this substance--yeast

In the first place, I should like to call your attention to a fact hich the whole of you are, to begin with, perfectly acquainted, I ar, any liquid which is for out the succulent parts of the fruits of plants, or a mixture of honey and water, if left to itself for a short tie No , yet after a few hours, or at ins to be turbid, and by-and-by bubblesyellowish foam or scurees, a similar kind of matter, which we call the ”lees,” sinks to the botto stuff, that we call the scu until it reaches a certain amount, and then it stops; and by the time it stops, you find the liquid in which this matter has been forin with it was a ht be the plant fro ar; but by the ti to you is accomplished the liquid has become completely altered, it has acquired a peculiar sained the property of intoxicating the person who drinks it Nothing can becan be less innocent, if taken in excess, as you all know, than those ferain, if you notice that bubbling, or, as it were, seething of the liquid, which has accompanied the whole of this process, you will find that it is produced by the evolution of little bubbles of air-like substance out of the liquid; and I dare say you all know this air-like substance is not like common air; it is not a substance which a man can breathe with impunity You often hear of accidents which take place in brewers' vats whenthat there was anything evil awaiting them And if you tried the experi, you would find that any small animal let down into the vessel would be siht lowered down into it would go out Well, then, lastly, if after this liquid has been thus altered you expose it to that process which is called distillation; that is to say, if you put it into a still, and collect the matters which are sent over, you obtain, when you first heat it, a clear transparent liquid, which, however, is sohter; it has a strong smell, and it has an acrid taste; and it possesses the sainal liquid, but in a ht to it, it burns with a bright flame, and it is that substance which we know as spirits of wine

Now these facts which I have just put before you--all but the last--have been known from extremely remote antiquity It is, I hope one of the best evidences of the antiquity of the hu the earliest records of all kinds of ot drunk We may hope that that must have been a very late period in their history Not only have we the record of what happened to Noah, but if we turn to the traditions of a different people, those forefathers of ours who lived in the high lands of Northern India, we find that they were not less addicted to intoxicating liquids; and I have no doubt that the knowledge of this process extends far beyond the limits of historically recorded ti to observe that all the nas to it, are nae, but in those older languages which go back to the times at which this country was peopled That word ”fermentation” for example, which is the title we apply to the whole process, is a Latin term; and a term which is evidently based upon the fact of the effervescence of the liquid Then the French, who are very fond of calling themselves a Latin race, have a particular word for ferment, which is 'levure' And, in the sa reference to the heaving up, or to the raising of the substance which is feret froe; but if we turn to the Saxon side, there are a number of names connected with this process of fermentation For example, the Gerahren;” and they call anything which is used as a fereest,” and finally in low German, ”yest”; and that word you know is the word our Saxon forefathers used, and is almost the same as the hich is commonly employed in this country to denote the co So they have another name, the word ”hefe,” which is derived fronifies to raise up; and they have yet a third name, which is also one common in this country (I do not knohether it is common in Lancashi+re, but it is certainly very common in the Midland countries), the word ”barnifies to raise or to bear up

Bar borne up; and thus there is much more real relation than is commonly supposed by those who make puns, between the beer which a man takes down his throat and the bier upon which that process, if carried to excess, generally lands hi up; the one thing is borne upon men's shoulders, and the other is the fer place in itself

Again, I spoke of the produce of fermentation as ”spirit of wine” Nohat a very curious phrase that is, if you come to think of it The old alche as if it had the sa itself as a man's spirit is supposed to have to his body; and so they spoke of this fine essence of the fer the spirit of the liquid Thus cae, in virtue of which you apply precisely the sain! And then there is still yet one other most curious piece of nomenclature connected with this matter, and that is the word ”alcohol”

itself, which is now so fainally meant a very fine powder The women of the Arabs and other Eastern people are in the habit of tinging their eyelashes with a very fine black pohich is made of antimony, and they call that ”kohol;” and the ”al” is simply the article put in front of it, so as to say ”the kohol” And up to the 17th century in this country the word alcohol was enify any very fine powder; you find it in Robert Boyle's works that he uses ”alcohol” for a very fine subtle powder But then this na very fine and very subtle came to be specially connected with the fine and subtle spirit obtained froar; and I believe that the first person who fairly fixed it as the proper nareat French chemist Lavoisier, so comparatively recent is the use of the word alcohol in this specialised sense

So eneral introduction to the subject on which I have to speak to-night What I have hitherto stated is sie, which everybody may acquaint hie is not any kind of conjuration, as people sometimes suppose, but it is simply the application of the sae, carried out, if I e which is uncommon And all that we kno of this substance, yeast, and all the very strange issues to which that knowledge has led us, have simply come out of the inveterate habit, and a very fortunate habit for the hu content until they have routed out all the different chains and connections of apparently simple phenomena, until they have taken them to pieces and understood the conditions upon which they depend I will try to point out to you nohat has happened in consequence of endeavouring to apply this process of ”analysis,” as we call it, this teazing out of an apparently simple fact into all the little facts of which it isto the barm or the yeast; secondly, what has come of the attempt to ascertain distinctly what is the nature of the products which are produced by fermentation; then what has come of the attempt to understand the relation between the yeast and the products; and lastly, what very curious side issues if I may so call them--have branched out in the course of this inquiry, which has now occupied so was to make out precisely and clearly as the nature of this substance, this apparently mere scum and mud that we call yeast And that was first commenced seriously by a wonderful old Dutchman of the nao, and as the first person to invent thoroughly trustworthy h powers Now, Leeuwenhoek went to work upon this yeast h powers of the microscope, he discovered that it was no ht at first suppose, but that it was a substance rains, each of which had just as definite a forh it was vastly s more than the two-thousandth of an inch in dia, and the very smallest of these particles were not more than the seven-thousandth of an inch in diameter Leeuwenhoek saw that this muddy stuff was in reality a liquid, in which there were floating this iated in heaps and lumps and some of them separate

That discovery remained, so to speak, dormant for fully a century, and then the question was taken up by a French discoverer, who, paying great attention and having the advantage of better instrus anddiscovery that they were bodies which were constantly being reproduced and growing; than when one of these rounded bodies was once forive off a little bud frorew out until it had attained the full size of the first, and that, in this way, the yeast particle was undergoing a process of , just as effectual and just as co; and thus this Frenchniard de la Tour, arrived at the conclusion--very creditable to his sagacity, and which has been confir since--that this apparently muddy refuse was neitherplants, growing and ary fluid in which the yeast is formed And from that time forth we have known this substance which forms the scum and the lees as the yeast plant; and it has received a scientific na of it, and which I will therefore give you--namely, ”Torula” Well, this was a capital discovery The next thing to do was to make out how this torula was related to the other plants I won't weary you with the whole course of investigation, but I may sum up its results, and they are these--that the torula is a particular kind of a fungus, a particular state rather, of a fungus or ive rise to this torula condition, to a substance which is not distinguishable from yeast, and which has the same properties as yeast--that is to say, which is able to decoar in the curious way that we shall consider by-and-by So that the yeast plant is a plant belonging to a group of the Fungi,in this very reary fluid which is, so to speak, the nidus or home of the yeast

That, in a feords, is, as far as investigation--by the help of one's eye and by the help of the microscope--has taken us But now there is an observer whose methods of observation are h it be aided by the microscope; a man who sees indirectly further than we can see directly--that is, the chemist; and the chemist took up this question, and his discovery was not less remarkable than that of the microscopist The che co, like a bladder, inside which is a peculiar soft, semifluid material--the chemist found that this outer bladder has the same composition as the substance of wood, that material which is called ”cellulose,” and which consists of the eleen But then he also found (the first person to discover it was an Italian chemist, named Fabroni, in the end of the last century) that this inner , which constitutes the yeast plant, was a substance containing the eleen; that it hat Fabroni called a vegeto-animal substance, and that it had the peculiarities of what are coain was an exceedingly relected for a tireat chemists of modern times, and they, with their delicate methods of analysis, have finally decided that, in all essential respects, the substance which forms the chief part of the contents of the yeast plant is identical with the material which forms the chief part of our own muscles, which forms the chief part of our own blood, which for; that, in fact, although this little organis but a plant, yet that its active living contents contain a substance which is called ”protein,” which is of the same nature as the substance which foranism whatever

Noe come next to the question of the analysis of the products, of that which is produced during the process of fer of the 16th century, in the times of transition between the old alchemy and the modern chemistry, there was a remarkable man, Von Helmont, a Dutchman, who saw the difference between the air which co and coas,” and he called this kind of gas ”gas silvestre”--so to speak gas that is wild, and lives in out of the way places--having in his mind the identity of this particular kind of air with that which is found in soation going on, it was discovered that this substance, then called ”fixed air,” was a poisonous gas, and it was finally identified with that kind of gas which is obtained by burning charcoal in the air, which is called ”carbonic acid” Then the substance alcohol was subjected to examination, and it was found to be a coar which was contained in the fer liquid was examined and that was found to contain the three eleen So that it was clear there were in sugar the fundamental elements which are contained in the carbonic acid, and in the alcohol And then careat chemist Lavoisier, and he examined into the subject carefully, and possessed with that brilliant thought of his which happens to be propounded exactly apropos to this matter of fermentation--that no es its fores its coar which was subjected to ferht of the sugar was represented by the carbonic acid produced; that in other words, supposing this tuar, that the action of feroing away in the shape of carbonic acid, and the other half going away in the shape of alcohol Subsequent inquiry, careful research with the refinements of modern chemistry, have been applied to this problem, and they have shown that Lavoisier was not quite correct; that what he says is quite true for about 95 per cent of the sugar, but that the other 5 per cent, or nearly so, is converted into two other things; one of them, matter which is called succinic acid, and the other lycerine, which you all kno as one of the coot to the end of this refined analysis yet, but at any rate, I suppose I may say--and I speak with some little hesitation for fear my friend Professor Roscoe hereupon his province--but I believe I may say that noe can account for 99 per cent at least of the sugar, and that 99 per cent is split up into these four things, carbonic acid, alcohol, succinic acid, and glycerine

So that it ar whatever disappears, and that only its parts, so to speak, are re-arranged, and if any of it disappears, certainly it is a very small portion