It will be noticed from the same figure on Plate LV. that a new acquisition was obtained, in the form of a fresh fungoid growth; and this circumstance is important in showing the length of time that spores may lie dormant in a solution before they become developed. There can hardly be a doubt that the spores which gave rise to this new form of fungus were originally present in the malt extract from which the mould had been taken, and that they remained inactive until the process of decomposition in the organic matter had reached a point which perhaps was not only favourable to, but tended to stimulate their development.

This, I believe, may be taken as an illustration of the difficulty that is experienced in making experiments with grain extracts, which are infested with animals and germs of various kinds to an extent that is something marvellous.

A quantity of mould from lemon juice was next obtained, and added to a solution containing 14 per cent. of glucose, and placed in the same chamber in which the preceding experiment was conducted. On the sixth day the sample was found to contain 0.91 per cent. of alcohol, and on the twenty-third day 8.44 per cent. of alcohol and 24 per cent. of acid.

This mould was extremely persistent, and maintained its position on the surface of the liquid throughout the fermentation; while the mould obtained from the malt became in a short time broken up and diffused throughout the sample.

It is worth noting in the case of the lemon-juice mould, and I have remarked the same thing in natural wine fermentations, that the quantity of alcohol produced fully represents the percentage of glucose; whereas in the case of the malt mould the quantity of alcohol produced is less than it ought to be according to the proportion of the glucose present.

In Fig. 7, Plate LV., is represented a specimen of the cells or spores taken from the residue at the bottom of the flask.

A sample of pus was next introduced into a solution containing 7 per cent. of glucose, and the sample was placed in a chamber kept at a temperature of upwards of 70° Fahr.

On the seventh day the sample was found to contain small transparent cells or spores, and flocculent masses of mycelium were observed floating in the liquid.

At the expiration of sixteen days the sample was found to contain 0.65 per cent. of alcohol, and ⚫06 per cent. of acid; and it is somewhat remarkable how free the sample was from microscopic animals.

The mycelium and spores produced by the pus are represented in Fig. 8, Plate LV., and it will be observed that they are almost identical in character with the mycelium and spores represented in Figs. 3 and 4, on Plate LV., and produced from the flour and malt albumen sugar solutions respectively.

The like description of fungoid mycelium development is occasionally met with in boiled malt extracts, but in albumen sugar solutions it usually occurs in an isolated form.

It is somewhat curious that this fungoid development in albumen sugar solutions should resemble so closely in character the development of the micrococcus in Hydrophobia in one of its stages of cultivation by Dr. Hallier.

From these and the other results which I have obtained it would appear that many fungoid developments in sugar solutions tend to produce alcohol and carbonic acid gas, but the proportion of alcohol produced within a given time by various fungi differs greatly.

In this lies the great distinction between the yeast plant and other fungoid developments, the yeast plant usually makes its appearance in three or four days, and it sets to work with an extraordinary degree of energy producing alcohol in great abundance.

There appears to be a kind of localized action with most fungoid growths in sugar solutions, whereas the action of the yeast plant is general, and it seems to be essential that the material upon which it depends for nourishment should be in solution.

Malt and Grape Yeast Plants.-Various comparative experiments have been made to determine the relative fermentative properties of the yeast plants of malt and the grape.

A cane sugar solution capable of yielding 17.5 per cent. of alcohol was prepared, and brewers' pressed yeast was then added in the proportion of 2000 grains to the half-gallon, and at different stages of the fermentation fresh quantities of yeast were added. On the ninth day the sample contained 12 32 per cent. of alcohol, on the twelfth 14 15, on the sixteenth 15 57, and on the nineteenth day 15 79, and at the end of thirty-six days 15 91.

It will be seen that during the first nine days alcohol was produced at a rate over 1 per cent. each day, but that its production from that time was extremely slow, and that practically on the sixteenth day, when the sample contained 15 57 per cent., the vitality of the yeast cells was suspended.

When the extreme point is nearly reached the cells become contracted, but when transferred to a fresh sugar solution and placed in favourable conditions they soon recover and begin to work afresh with their usual vigour. Every precaution was taken to guard against loss of alcohol by diffusion, as it was found that when about 12 per cent. of alcohol was reached the loss of alcohol in an open vessel was equal to the quantity generated.

Several malt extracts were prepared and the saccharine value thereof was raised to certain points by the addition of glucose, and allowed to ferment naturally.

The malt extracts were prepared by infusion at a temperature of about 180° Fahr., and from what has been already stated I need

hardly refer to the difficulty which was experienced in obtaining a pure healthy fermentation from a malt extract prepared at this temperature, although the infusion was maintained at that temperature for upwards of three hours, and the addition of 30 per cent. of glucose operated as an antiseptic.

The most successful malt wort fermentation was one in which the glucose, including that naturally present in the malt extract, amounted to over 36 per cent., and the fermentation was conducted at a temperature ranging from 63° to 70° Fahr. No fermentation was visible until the sixth day, when a number of hazy cells, which indicate the commencement of fermentation, made their appearance. Soon after this the fermentation began to be brisk, and by the ninth day 10.96 per cent. of alcohol had been generated, or within 1.35 per cent. of the quantity produced in the same time in the cane sugar solution by the addition of yeast. Now this fact, is very interesting, as it serves to show the great facility with which glucose, as compared with cane sugar, is resolved into alcohol and carbonic acid gas, and to indicate the large additional expenditure of force which must be required to effect the two transformations in cane sugar by the fermentative process.

From the ninth day the fermentation began to abate; in the three days following 2.83 per cent. of alcohol was produced, and in the next sixteen days 2 60, making altogether 16 35 per cent. of alcohol, which is the highest amount that has been reached in the fermentation of malt extracts prepared in the way described. It should be noted, however, that in this case the fermented liquid contained over 7 per cent. of glucose, and that it is probable if the proportion of glucose had been less a higher percentage of alcohol might have been produced.

It may be proper to mention that from a series of experiments it has been found that alcohol and sugar combine to act as an antiseptic, and that by increasing the percentage of sugar the fermentative power of the liquid is proportionately decreased. It is upon this property of their combined action that a less quantity of proof spirit is required to be present in liqueur than in ordinary wines, to prevent their deterioration. For example, a properly-made liqueur wine, containing 20 per cent. of glucose and about 14 per cent. of alcohol would be perfectly safe for keeping, or indeed for removing, to any part of the world; but if the wine contained only 14 per cent. of glucose, to render it proof against deterioration the proportion of alcohol would require to be increased to about 17 per cent.

A specimen of the exhausted yeast cells taken from the fermented wort in which the highest percentage of alcohol was produced, will be seen on Plate LV., Fig. 9; and it will be noticed that the cells are very granular and much aggregated, properties which are to some extent characteristic of the exhausted malt ferment.

The experiments with grape "must" had to be made chiefly with English hot-house grapes, and as these were gathered in the months of December and January, the percentage of glucose was, as might have been expected, low; but, as in the case of the malt extract, the percentage was increased to the required point by the addition of pure glucose.

In the fermentation of grape "must" the chief enemy to be encountered is the development of mould spores, which, when once established, affect the flavour of the wine, and in many instances render it unfit for use as a beverage.

As an illustration of this a sample of wine was made from English hot-house grapes, and it would have been a very fair sample considering the conditions under which it was made, were it not that it possessed a musty odour. On the second day after the juice was placed in the chamber for fermentation, a white mould, Oidium Tuckeri, formed on the surface, and attempts were made to remove it, but in vain, as it rapidly diffused itself throughout the juice. On the following day the yeast cells made their appearance in great numbers, and they soon took possession of the field and rapidly suppressed the further development of the mould on the surface. It is true that the ferment afterwards was never pure, but still the wine yeast cells continued to work until they had produced upwards of 17 68 per cent. of alcohol.

The grape ferment according to my observations is extremely pure and homogeneous in character, and if the conditions are favourable for its growth and development it does its work well. It works with great steadiness and possesses a degree of persistence which does not belong, at least so far as I have seen, to the beer ferment.

In most of the wine fermentation experiments the husks were nearly all fermented with the juice, and everything was adopted which was thought would add to the fermentative power of the "must." In one instance the percentage of glucose was made up to about 36 per cent., and the juice was placed for fermentation in a chamber at a temperature of 65° Fahr. On the fourth day fermentation was visible, and on the tenth day 10.20 per cent. of alcohol had been generated; on the twenty-third day 18 54 per cent.; and at the end of ten days more the percentage had increased to 18 65 per cent., which is the highest point that has been reached in natural wine fermentations. The cells, notwithstanding the amount of work which they had performed, were even at this point bright and globose, and maintained their entirety.

A sample of these exhausted cells was taken a few days ago from the residue of a sample of the wine, and their present appearance after the lapse of five months will be seen on Plate LV., Fig. 10.

Microscopical

Another sample of juice was similarly treated to the foregoing, but fermented at a temperature ten degrees higher. The fermentation in this case was visible on the third day, and at the end of fourteen days 17.40 per cent. of alcohol had been generated in the "must ;" and at the expiration of a month, the temperature being continuously maintained at 75° Fahr., the proportion of alcohol had increased to 18 26 per cent. The yeast cells were much shrivelled, and some appeared to have burst; in fact, altogether the higher temperature was clearly less favourable for good, steady, healthy fermentation.

In another wine experiment the percentage of glucose in the juice was made up to about 40 per cent., and the fermentation was conducted at a temperature of about 65° Fahr.

The juice was prepared from the same sample of grapes as that employed in the first wine experiment above described, and the two samples were fermented side by side.

The fermentation did not start so soon as in the other wine experiments, the large percentage of glucose having delayed the development of the yeast cells nearly two days beyond the usual time. On the tenth day 10 62 per cent. of alcohol had been generated in the juice, and at the end of a month the percentage of alcohol had increased to 17 26 per cent., being 1.39 per cent. less than the quantity produced in the sample which contained the lower percentage of glucose.

It is upon this and similar results obtained under the like circumstances that the statement above is founded, viz. that the alcohol and sugar combine to act as an antiseptic.

In all these cases the wine ferment has the advantage, and has proved itself to possess greater fermentative powers than the malt ferment.

From the results obtained in the fermentation of grape juice I cannot refrain from expressing my opinion that it would be an improvement in the manufacture of wines if, where the percentage of glucose in grape juice is low, an addition of grape sugar were made before or during the fermentation of the "must."

The addition of the sugar would assist in exhausting the juice of its fermentative power which is generally in excess of the glucose naturally present, and tend to prevent acetous fermentation, and the development of obnoxious fungoid growths. It would also have the effect of obviating to a great extent the necessity for fortifying many descriptions of wine, and impart to them a greater body by reducing the proportion of water added and which is present in the alcohol used for fortifying.

In selecting, however, samples of glucose or sugar for this purpose great care would require to be exercised, to ensure their freedom from microscopic animals and germs.