New York turn out very good
instruments, and if a physician purchases an inferior one, the fault is
his own.

Two different currents are required for the baths, viz. 1)--The
galvanic, which may be employed either in the constant or interrupted
(by means of a rheotome) form; and 2)--the faradic or induced current.
Several manufacturers of this city turn out good and serviceable faradic
instruments. Those which I have been in the habit of using for some
years past are manufactured by the Galvano-Faradic Manufacturing
Company, and they have given me unvarying satisfaction. By means of a
recently introduced attachment to their batteries, termed the "fine
adjustment," a current of exquisite "fineness" (rapidity of
interruption) is obtained, thus removing the only inferiority that has
heretofore distinguished American from the best imported instruments.
The instrument is very easy of management, and its liability to get out
of order very small.

As however the galvanic current is of vastly greater importance in a
therapeutic respect, than the faradic, so also much greater care is
required in the choice of a galvanic than a faradic battery. In making
choice of a galvanic battery, we have to consider its relative quantity,
intensity, constancy, permanency, economy of running expenses, and
facility of management. We cannot be guided here by the same
considerations that guide us in the choice of a battery for office use,
where the _seances_ are usually brief and the elements taxed not nearly
so much as in the administration of baths. It is not within the scope of
this work to enter into a description of the various galvanic batteries
that are in use. Neither do I believe that, in a therapeutic sense,
there is much difference between the various batteries ordinarily found
described in text-books on electro-therapeutics.

Where the battery is to be stationary, a zinc-copper battery, such as
the Hill battery for example, is preferable both on account of its
constancy and the economy of running it. Of this there should be fully
sixty cells, communicating with the bath through a current selector, by
means of which the current from any desired number of cells can be
obtained. The electro-susceptibility of different individuals varies to
such an extent that this is absolutely necessary. Where a portable
battery is desired, the Stoehrer zinc-carbon battery will be found the
most useful.

I have mentioned these two batteries simply