186 MICROSCOPY. 
development where nerves run parallel to one another are men- 
tioned by the author as incompatible with this theory; though it 
is not inconceivable that such insulation should be as essential 
to other vibrations as to electrical movements. 
That nerve fibre is a peculiarly vital form of tissue, pervaded 
by some exceptional form of force nowhere else present, seems en- 
tirely to want confirmation. 
That the nerve current is ordinary electricity, transmitted through 
the beautifully insulated axis cylinder, though not proved, is con- 
sidered more than probable, notwithstanding the somewhat incon- 
gruous result obtained by rough experiments, such as transmitting 
more powerful currents through mutilated nerves, or through : 
nerves and other tissues after the post mortem changes, or at a 
rate slower than through copper wire, no allowance being made for 
the less perfect conducting power of a moist fibrous cord. No one 
has disproved the electrical character of the nerve current, while 
such character is strongly supported by a multitude of well deter- 
mined facts, especially those connected with the electrical organs 
of some of the lower animals, where electricity is set free in special 
organs rich in nerves but not essentially different from other nerve 
organs. 
How the course of the electrical current is directed and varied, 
and how subjected to the control of the will, are independent 
questions not yet answered. 
Insects’ FEET as CARRIERS or Dirt. — Prof. W. Kletzinsky, ` 
of Vienna, has detected with the microscope an abundance of for- 
eign particles in pure glycerine into which flies had stepped and 
from which they had succeeded in freeing themselves; thus vindi- 
cating the belief that flies may become carriers of contagious 
diseases. 
CIRCULATION IN Insects. — Mr. R. King read an interesting 
paper on this subject at the Dubuque meeting of the American 
Association. By a microscopical study of insects during periods 
of dormancy or hibernation, some forms of larve, especially, 
being so transparent that the microscope gains a perfect view of 
their internal organs without interfering with them, he is satisfied 
that there is nio circulation while the insect is at absolute rest, and 
_ that the ordinary circulation in insects is entirely the result of the 
voluntary muscular activity of the creatures. 
