Part 1 (2/2)

Now these are the facts of the case There is the fact of the growth of the yeast plant; and there is the fact of the splitting up of the sugar

What relation have these two facts to one another?

For a very long tireat matter of dispute The early French observers, to do them justice, discerned the real state of the case, namely, that there was a very close connection between the actual life of the yeast plant and this operation of the splitting up of the sugar; and that one was in soation subsequently has confirinal idea It has been shown that if you take any measures by which other plants of like kind to the torula would be killed, and by which the yeast plant is killed, then the yeast loses its efficiency But a capital experiuished man, Helmholz, who performed an experiment of this kind He had two vessels--one of them ill suppose full of yeast, but over the bottoht be, was tied a thin filh that thin filo, but the solid parts would be stopped behind; the torula would be stopped, the liquid parts of the yeast would go And then he took another vessel containing a ferar, and he put one inside the other; and in this way you see the fluid parts of the yeast were able to pass through with the utet through at all And he judged thus: if the fluid parts are those which excite ferar will not fer quite clearly, that an i torula was absolutely necessary to excite this process of splitting up of the sugar This experiment was quite conclusive as to this particular point, and has had very great fruits in other directions

Well, then, the yeast plant being essential to the production of ferain, was another great proble, you have, under ordinary circumstances in eather, ar, or any foretable juice to the air, in order, after a comparatively short time, to see all these phenoestion is, that the torula has been generated within the fluid In fact, it seems at first quite absurd to entertain any other conviction; but that belief would inning of this century, in the vigorous times of the old French wars, there was a Monsieur Appert, who had his attention directed to the preservation of things that ordinarily perish, such as etables, and in fact he laid the foundation of ourmeats; and he found that if he boiled any of these substances and then tied them so as to exclude the air, that they would be preserved for any time He tried these experiments, particularly with the must of wine and with the wort of beer; and he found that if the wort of beer had been carefully boiled and was stopped in such a way that the air could not get at it, it would never ferain, beca of experiments, with this ultimate result, that if you take precautions to prevent any solidinto the must of wine or the wort of beer, under these circumstances--that is to say, if the fluid has been boiled and placed in a bottle, and if you stuff the neck of the bottle full of cotton wool, which allows the air to go through and stops anything of a solid character however fine, then you may let it be for ten years and it will not ferive the air free access, then, sooner or later fermentation will set up And there is no doubt whatever that fermentation is excited only by the presence of some torula or other, and that that torula proceeds in our present experience, fro torulae These little bodies are excessively light You can easily ihtly heavier than water, and not more than the two-thousandth or perhaps seven-thousandth of an inch in dia like motes in the sunbeam; they are carried about by all sorts of currents of air; the great majority of theary solution, immediately enter into active life, find there the conditions of their nourishive rise to any quantity whatever of this substance yeast And, whatever eneration,” as it is called in regard to all other kinds of living things, it is perfectly certain, as regards yeast, that it always owes its origin to this process of transportation or inoculation, if you like so to call it, froanism; and so far as yeast is concerned, the doctrine of spontaneous generation is absolutely out of court

And not only so, but the yeast must be alive in order to exert these peculiar properties If it be crushed, if it be heated so far that its life is destroyed, that peculiar power of fermentation is not excited

Thus we have come to this conclusion, as the result of our inquiry, that the ferar into alcohol and carbonic acid, glycerine, and succinic acid, is the result of nothing but the vital activity of this little fungus, the torula

And now coly difficult inquiry--how is it that this plant, the torula, produces this singular operation of the splitting up of the sugar? Fabroni, to whoined that the effervescence of fermentation was produced in just the same way as the effervescence of a sedlitz powder, that the yeast was a kind of acid, and that the sugar was a combination of carbonic acid and some base to form the alcohol, and that the yeast combined with this substance, and set free the carbonic acid; just as when you add carbonate of soda to acid you turn out the carbonic acid But of course the discovery of Lavoisier that the carbonic acid and the alcohol taken together are very nearly equal in weight to the sugar, completely upset this hypothesis Another vieas therefore taken by the French chemist, Thenard, and it is still held by a very eminent chemist, M Pasteur, and their view is this, that the yeast, so to speak, eats a little of the sugar, turns a little of it to its own purposes, and by so doing gives such a shape to the sugar that the rest of it breaks up into carbonic acid and alcohol

Well, then, there is a third hypothesis, which is , which denies either of the other two, and which declares that the particles of the sugar are, as it were, shaken asunder by the forces at work in the yeast plant Now I a to take you into these refinements of chemical theory, I cannot for a moment pretend to do so, but I y Suppose you coar to a card house, and suppose you co near the card house, then Fabroni's hypothesis was that the child took half the cards away; Thenard's and Pasteur's hypothesis is that the child pulls out the botto's hypothesis is that the child comes by and shakes the table and tumbles the house down I appeal to my friend here (Professor Roscoe) whether that is not a fair state thus, as far as I can, discussed the general state of the question, it remains only that I should speak of some of those collateral results which have coation of yeast I told you that it was very early observed that the yeast plant consisted of a bag made up of the same material as that which composes wood, and of an interior semifluid mass which contains a substance, identical in its composition, in a broad sense, with that which constitutes the flesh of animals Subsequently, after the structure of the yeast plant had been carefully observed, it was discovered that all plants, high and low, are s or ”cells,” as they are called; these bags or cells having the co the sa, as the sac of the yeast plant, and having in their interior aa matter of the same nature as the protein substance of the yeast plant And therefore this remarkable result came out--that however much a plant may differ from an animal, yet that the essential constituent of the contents of these various cells or sacs of which the plant is enous protein matter, is the saradually discovered, but it was found that these semifluid contents of the plant cell had, in many cases, a remarkable power of contractility quite like that of the substance of anio, namely, about the year 1846, to the best of o Von Mohl, conferred upon this substance which is found in the interior of the plant cell, and which is identical with the ain contains an animal substance similar to that of which we ourselves are made up--he conferred upon this that title of ”protoplasreat deal of trouble since! I beg particularly to say that, because I find many people suppose that I was the inventor of that term, whereas it has been in existence for at least twenty-five years And then other observers, taking the question up, ca from this basis of the yeast), that the differences between animals and plants are not so much in the fundamental substances which compose them, not in the protoplasm, but in the manner in which the cells of which their bodies are built up have become modified There is a sense in which it is true--and the analogy was pointed out very o by some French botanists and chemists--there is a sense in which it is true that every plant is substantially an enor to a certain extent its own independent life And there is a sense in which it is also perfectly true--although it would be iive the statement to you with proper qualifications and limitations on an occasion like this--but there is also a sense in which it is true that every aniation of minute particles of protoplasm, comparable each of them to the individual separate yeast plant And those who are acquainted with the history of the wonderful revolution which has been worked in our whole conception of thesethat the first gerrow and fructify by the study of the yeast plant, which presents us with living matter in almost its simplest condition

Then there is yet one last andof this yeast question There is one direction probably in which the effects of the careful study of the nature of fermentation will yield results more practically valuable to mankind than any other Let inning of this lecture Suppose that I had here a solution of pure sugar with a little mineral matter in it; and suppose it were possible for le, solitary yeast cell,no more perhaps than the three-thousandth of an inch in diaer than one of those little coloured specks of ht of which it would be difficult to express in the fraction of a grain--and put it into this solution Frole one, if the solution were kept at a fair teenerated, in the course of a week, enough torulae to form a scue the perfectly tasteless and entirely harnated with the poisonous gas carbonic acid, inated with the poisonous substance alcohol; and that, in virtue of the changes worked upon the sugar by the vital activity of these infinitesimally small plants Now you see that this is a case of infection And from the time that the phenomenon of fermentation were first carefully studied, it has constantly been suggested to theastoundingly siation of ferion, and the phenoion

Out of this suggestion has grown that reerreata certain life of their own, and which are capable of being trans to another, exactly as the yeast plant is capable of being transmitted from one tumbler of saccharine substance to another And that is a perfectly tenable hypothesis, one which in the present state of ht to be absolutely exhausted and shown not to be true, until we take to others which have less analogy in their favour And there are some diseases most assuredly in which it turns out to be perfectly correct There are sonant carbuncle which have been shown to be actually effected by a sort of fermentation, if I may use the phrase, by a sort of disturbance and destruction of the fluids of the anianisms which are the cause of this destruction and of this disturbance; and only recently the study of the phenoht in this direction, tending to show by experieneral character as that to which I referred as perfor analogy between the contagion of that healing disease and the contagion of destructive diseases For it has been ations carried on in France and in this country, that the only part of the vaccineon its influence in the organism of the child who is vaccinated, is the solid particles and not the fluid By experienious kind, the solid parts have been separated from the fluid parts, and it has then been discovered that you may vaccinate a child as much as you like with the fluid parts, but no effect takes place, though an excessively small portion of the solid particles, the ive rise to all the phenomena of the cow pock, by a process which we can co but the transmission of fermentation from one vessel into another, by the transport to the one of the torula particles which exist in the other

And it has been shown to be true of some of the most destructive diseases which infect animals, such diseases as the sheep pox, such diseases as that landers, that in these, also, the active power is the living solid particle, and that the inert part is the fluid However, do not suppose that I ay too far I do not mean to say that the active, solid parts in these diseasedyeast plants; but, so far as it goes, there is a y between the two; and the value of the analogy is this, that by following it out we may some tiated, just as we understand, now, about feres which afflict the huely alleviated

This is the conclusion of the statements which I wished to put before you You see we have not been able to have any accessories If you will come in such numbers to hear a lecture of this kind, all I can say is, that diagrah for you, and that it is not possible to show any experiments illustrative of a lecture on such a subject as I have to deal with Of course my friends the chemists and physicists are very much better off, because they can not only show you experiments, but you can smell them and hear them! But in my case such aids are not attainable, and therefore I have taken a simple subject and have dealt with it in such a way that I hope you all understand it, at least so far as I have been able to put it before you in words; and having once apprehended such of the ideas and simple facts of the case as it was possible to put before you, you can see for yourselves the great and wonderful issues of such an apparently homely subject