Part 23 (1/2)
FLASK A, WITHOUT AIR
January 21st--Fermentation commenced; a little frothy liquid issued fro days, fer the yeast mixed with the froth that was expelled into the as, we find that it was very fine, young, and actively budding
February 3rd--Fer itself by a nu froht The yeast was at the bottom in the form of a deposit
February 7th--Feruidly
February 9th--A very languid fer from the bottom of the flask
FLASK B, WITH AIR
January 21st--A sensible develop days, fermentation was active, and there was an abundant froth on the surface of the liquid
February 1st--All symptoms of fermentation had ceased
As the fer so very languid, and as that in B had been finished for several days, we brought to a close our two experiments on February 9th
To do this we poured off the liquids in A and B, collecting the yeasts on tared filters Filtration was an easythe yeasts under the microscope, immediately after decantation, we found that both of them remained very pure The yeast in A was in little clusters, the globules of which were collected together, and appeared by their well-defined borders to be ready for an easy revival in contact with air
As ht have been expected, the liquid in flask B did not contain the least trace of sugar; that in the flask A still contained some, as was evident frorainally contained three litres of liquid holding in solution 5 per cent of sugar, it follows that 150 graar had ferrains) in the flask A The weights of yeast after drying at 100 degrees C (212 degrees F) were--
For the flask B, with air1,970 grarararains--D C R]
The proportions were 1 of yeast to 76 of ferar in the first case, and 1 of yeast to 89 of ferar in the second
Fro consequences may be deduced:
1 The fermentable liquid (flask B), which since it had been in contact with air, necessarily held air in solution, although not to the point of saturation, inaserreater than that yielded by the liquid which contained no air at all (flask A) or, at least, which could only have contained an exceedingly htly aerated fermentable liquid ferht or ten days it contained no ar; while the other, after twenty days, still contained an appreciable quantity
Is this last fact to be explained by the greater quantity of yeast formed in B? By no means At first, when the air has access to the liquid, ar disappears, as we shall prove immediately; nevertheless the yeast formed in contact with the air is more active than the other Ferlobules, and then to the continued life of those globules once forlobules have at their disposal during their forescent, and, as a consequence of this last quality, the ar We shall hereafter revert to these facts
3 In the airless flask the proportion of yeast to sugar was 1/59; it was only 1/79 in the flask which had air at first
The proportion that the weight of yeast bears to the weight of the sugar is, therefore, variable, and this variation depends, to a certain extent, upon the presence of air and the possibility of oxygen being absorbed by the yeast We shall presently show that yeast possesses the power of absorbing that gas and een st the number of food-stuffs that may be assien in yeast, as well as the oxidations resulting from it, have the most marked effect on the life of yeast, on the multiplication of its cells, and on their activity as ferar, whether ien or air
In the preceding experiment, conducted without the presence of air, there is one circumstance particularly worthy of notice
This experiment succeeds, that is to say, the yeast sown in the en develops, only when this yeast is in a state of great vigour We have already explained theof this last expression But ish now to call attention to a very evident fact in connection with this point We inate a fermentable liquid; yeast develops and fermentation appears This lasts for several days and then ceases Let us suppose that, from the day when fermentation first appears in the production of a radually increases until it whitens the surface of the liquid, we take, every twenty-four hours, or at longer intervals, a trace of the yeast deposited on the botto fresh fer these fermentations all under precisely the same conditions of temperature, character and volued tiinal fer that the first signs of action in each of our series of second fermentations appear always later and later in proportion to the length of tiinal fermentation In other words, the tierms and the production of that amount of yeast sufficient to cause the first appearance of fer cells, and is longer in proportion as the cells are further removed from the period of their formation It is essential, in experiments of this kind, that the quantities of yeast successively taken should be as nearly as possible equal in weight or volume, since, celeris paribus, ferer the quantity of yeast enation
If we compare under the microscope the appearance and character of the successive quantities of yeast taken, we shall see plainly that the structure of the cells undergoes a progressive change
The first sainal ferer than those later on, and possessing a rely thin, the consistency and softness of their protoplasranular contents appear in the form of scarcely visible spots The borders of the cells soon beco; their protoplasranulations an, in the states of infancy and old age, should not differ , taken in their extrees in the cells, after they have acquired their normal form and volume, clearly demonstrate the existence of a cheht increases, although in volue, a fact that we have often characterized as ”the continued life of cells already formed” We may call this work a process of maturation on the part of the cells, als in general, which continue to live for a long time, even after they have beco after their volu so, it is evident, we repeat, that, to multiply in a feren, the cells of yeast , full of life and health, and still under the influence of the vital activity which they owe to the free oxygen which has served to form them, and which they have perhaps stored up for a time When older, they reproduce theradually becoe and monstrous forms A little older still, they reen This is not because they are dead; for in general they may be revived in a marvellous manner in the same liquid if it has been first aerated before they are sown It would not surprise us to learn that at this point certain preconceived ideas suggest themselves to the mind of an attentive reader on the subject of the causes that e phenonorance hides under the expressions of YOUTH and AGE; this, however, is a subject which we cannot pause to consider here
At this point we reat importance--that in the operations of the brewer there is always a tiorous youth of which we have been speaking, acquired under the influence of free oxygen, since all the worts and the yeasts of commerce are necessarily nated en The yeast ias and acquires a state of freshness and activity, which permits it to live afterwards out of contact with air, and to act as a ferment Thus, in ordinary brewery practice, we find the yeast already forns of fermentation have made their appearance In this first phase of its existence, yeast lives chiefly like an ordinary fungus