in the whole list of
infectious diseases are two, epidemic cerebro-spinal meningitis (spotted
fever), and tetanus (lockjaw). Both of these have an extraordinary and
deadly preference for the nervous system from the very start, and this
is what gives them their frightful mortality and discouraging outlook.
Even of this small number of exceptions, we are not altogether certain
as to epidemic meningitis, inasmuch as we do not know how long the germ
may have existed in the other tissues of the body before it succeeded in
working its way to and attacking the brain and spinal cord.

The case of tetanus, however, is perfectly clear in this regard, and
exceedingly interesting, inasmuch as it explains why a disease specially
involving the nervous system from the start is so excessively hard to
check or cure. The germ of the disease, long ago identified as one
having its habitat in farm or garden soils,--particularly those which
have been heavily fertilized with horse manure,--gets into the system
through a cut or scratch upon the surface, into which the soil is
rubbed. These infected cuts, for obvious reasons, are most frequently
upon the hands or feet.

Small doses of the organism have been injected into animals; then, when
they have recovered, larger ones, and so on, after the manner of the
bacillus of diphtheria, until a powerful antitoxin can be obtained from
their blood, very minute quantities of which will promptly kill the
bacilli in a test-tube. For seven or eight years past we have been
injecting this into every patient with tetanus that came under our
observation, but so far with very limited benefit, even though the
injections were made directly into the spinal cord, or brain substance.
The problem puzzled us for years, until finally Cattani stumbled upon
the explanation. While we had been supposing that the poison was
carried, as almost every other known poison is, through the
blood-vessels, or lymph-channels, to the heart and thence to the brain,
he clearly proved that it ran up the central axis of the nerve-trunks,
and consequently, when it had got once fairly started up this channel,
was as safe from the attack of any antitoxin merely present in the
general circulation and fluids of the body, as the copper of the
Atlantic cable is from the eroding action of the sea-water. If, in his
experimental animals, he carefully sought for the cut end of the
nerve-trunk in the wound that had been infected, and injected the