able to confirm these
results by a series of tests of the same gums in India, but have not yet
obtained information as to their behavior in the early part of the year.

The fermentation of natural gum solutions is accompanied by a decrease
in the viscosity of the liquid and the separation of a portion of the
gum in lumps. Apparently those gums which contain most sugar, as
indicated by their reduction of Fehling's solution, are the most
susceptible to this change. Oxalic acid is formed by the fermentation,
which by combination with the lime present renders the fermenting liquid
turbid, and also some volatile acid, probably acetic.

We have made some experiments with a gum which readily fermented--in a
week--as to the respective value of various antiseptics in retarding the
fermentation. Portions of the gum solutions were mixed with small
quantities of menthol, thymol, salol, and saccharin in alkaline
solution, also with boric acid, sodium phosphate, and potash alum in
aqueous solution. Within a week a growth appeared in a portion to which
no antiseptic had been added; the others remained clear. After over five
months the solutions were again examined, when the following results
were observed:

----------------------+-------------------------------------------
|
Antiseptics. | Solution after Five Months.
----------------------+-------------------------------------------
|
Menthol in KOH..... | Some growth at bottom, upper layer clear.
|
Thymol in KOH..... | Growth at top, gum white and opaque.
|
Salol in KOH........ | Growth at top, gum black and opaque
|
Saccharin in KOH ... | White growth at top.
|
Boric acid............| Remained clear; did not smell.
|
Sodium phosphate ... | Slight growth at top.
|
Potash alum......... | Slight growth at top.
----------------------+-------------------------------------------

The solution to which no antiseptic had been added was of course quite
putrid, and gave the reactions for acetic acid.

In the earlier part of this paper we have given a short account of the
chief characteristics of the more important gum substitutes. The
following additional notes may be of interest.

The ashes of most gum substitutes, consisting chiefly of dextrin, are
characterized by the high percen