516 
EDINBURGH MEETING. 
nections of one of these we know nothing, of the other we know that it is trebly- 
related, and that we can make it enter into two new relations. We can do this 
by uniting it to an acid, hydrochloric acid for instance, in which case the new 
relations are, one to hydrogen and one to chlorine; to use the old metaphor, it 
borrows from chlorine and invests in hydrogen. We cannot, however, compare 
the action of strychnia with that of its hydrochlorate, for a very slight induce¬ 
ment is all that is necessary to make chlorine call up its investment, and retire 
with an atom of hydrogen. To try the effect of addition we must add two new 
relations of a more stable kind. This is done by acting on strychnia, not with 
an acid, that is a compound of hydrogen, but with an ether or compound of 
methyl or ethyl, such as iodide of methyl or iodide of ethyl. Here the nitrogen 
borrows from iodine and invests in methyl or ethyl, and the resulting compound is 
so stable that it has no tendency to recur to its former state. These peculiar 
compounds were first studied chemically by How, and afterwards by Stahl- 
schmidt. The latter made some experiments with methyl-strychnium salts on 
rabbits, and came to the conclusion that they were quite inert. A more com¬ 
plete examination has shown that this is not exactly true, but that a still more 
remarkable change has been produced. Large doses (thirty grains) of the iodide 
of methyl-strychnium (the compound of strychnia with iodine and methyl) pro¬ 
duce no effect whatever when administered to a rabbit by the stomach ; fifteen 
grains, however, kill a rabbit when injected under the skin. In this case the 
symptoms are quite unlike those of strychnia poisoning; instead of violent 
tetanic convulsions, we observe a condition of general paralysis. Now it is im¬ 
portant that we should know how this paralysis is produced, and for this pur¬ 
pose we had recourse to a method which has been very successfully applied to 
the study of various poisons, especially “ urali ” or “ curare,” the South American 
arrow poison. To make this method of experimenting intelligible, I shall com¬ 
pare the nervous system to a set of telegraph-wires and offices. Let us suppose 
that every town in the country has two telegraph-offices, and that each is con¬ 
nected by a wire with the head office in London, one of the wires is used only 
for sending messages up to London, the other only for sending messages down, 
and there is no means of telegraphic communication between one country town 
and another, except through London. Let us further suppose that whenever a 
message from London is received in any town the town bell is rung; now if 
we give in a message at the Manchester office, intending it to go through London 
to every town in the country, and find that no bells are rung, it is obvious that 
something is wrong; it may be, first, that the apparatus at Manchester is out 
of order, so that the message was never sent; or, second, that the up wire from 
Manchester was broken or not insulated, so that the message never reached 
London ; or, third, that there was something wrong at the head office; or, 
fourth, that all the down wires were broken or not insulated; or, fifth, that 
something was wrong at all the receiving offices throughout the country; or, 
sixth, that the bells could not be rung. When a healthy frog is pinched any¬ 
where the animal jumps, a message is sent from the part of the skin pinched to 
the nerve-centres, and thence to all the muscles; but if we give the frog iodide 
of methyl strychnium a pinch produces no effect. As in the supposed tele¬ 
graphic case this result may be due to one of six causes,—first, the ends of the 
sensory nerves may be injured, so that the message is never sent from the place 
pinched; or, second, the sensory nerve-trunks may be paralysed, so that the 
message does not reach the nerve-centres; or, third, the nerve-centres may be 
so deranged that they do not send it on to the motor nerves; or, fourth, the 
motor nerve-trunks may be paralysed ; or, fifth, the terminations of the motor 
nerves may be injured, so that they do not communicate the stimulus to the 
muscular fibres; or, sixth, the muscular fibres themselves may be incapable of 
contracting. 
