shoe magnets may thus be
regulated in such a way as to form a perfectly astatic system in a
uniform field and to preserve an almost invariable zero, this being
something that it is very difficult to obtain with the ordinary
arrangement of needles, especially when a compensating magnet is used;
for, in such a case, one of the needles becomes more or less magnetized,
while the other becomes demagnetized, according to the position of the
compensating magnet.--_La Lumiere Electrique_.

* * * * *

HISTOLOGICAL METHODS.

A cat, dog, rabbit, or Guinea pig will furnish parts from which sections
can be cut for the study of histology. Whichever animal is selected
should be young and well developed. Put it under influence of chloroform,
and open into the cavity of the chest; make an incision into the right
ventricle, and allow the animal to bleed to death; cut the trachea and
inject the lungs with a solution of one and a half drachms of chromic
acid in one quart of water, care being taken not to overdistend the lung.
Tie the severed end to prevent the escape of the fluid, and carefully
remove the lung. It is a difficult thing to do this without rupturing it,
but with care and patience it can be done. Place the lungs in a solution
of the same strength as used for injecting; after fifteen or twenty hours
change it to a fresh solution, and allow it to remain for about a month,
and then change it to rectified spirits, in which it may remain until
required.

Cut the tongue into several transverse and longitudinal pieces, also the
small intestines, and put them into a solution of fifteen and one-half
grains chromic acid, thirty grammes bichromate of potash, and three pints
of water; change the solution the next day, and let them remain two weeks
and then place in spirits. Cut longitudinal and transverse portions of
the stomach and large intestines, wash in a weak solution of salt and
water, and put them in the same solution as used for the lungs, and treat
similarly.

Cut the kidneys longitudinally and transversely, and put them in a
solution of six and one-half drachms bichromate of potash, two and
one-half drachms sodium sulphate, one quart of water; change the solution
the next day, and at the end of four weeks transfer to alcohol. Wash the
inner surface of the bladder with salt and water, and after cutting it
longitudinally and transversely, put the sections in a solution of three
drachms