MR. J. PRIESTLEY ON THE PHYSIOLOGICAL ACTION OE VANADIUM. 553 
the nervous symptoms of poisoning took in them, the conclusions drawn apply primarily 
to those symptoms. 
Paralysis of voluntary motion may result from disorder of one or more of four sets of 
organs. It may be caused by some affection of the motorial end-plates of nerves in 
muscles, as in the case of poisoning by curare ; it may result from some interruption in 
the conducting apparatus by which impulse to contraction is conveyed from the centre 
to the muscle, as in the case of lesions of the cord or trunks of nerves due to mechanical 
or other causes ; it may be attributable to some alteration in the central nerve-cell from 
which the impulse to contraction (proximately) originates ; or it may be due to loss of 
irritability of muscular tissue, as in the case of poisoning by sulphocyanides. In para- 
lysis of reflex motion (which occurs in frogs, but not in other animals) the motor appa- 
ratus itself is not necessarily implicated, as such paralysis may be due to an affection 
of any one of the analogous parts of the afferent system, viz. peripheral organ (of 
sense), centripetal nerve-fibre, or central cell in which the impulse conveyed from the 
periphery is reflected. When, however, paralysis of reflex action is accompanied by 
paralysis of voluntary motion (as in the case of frogs poisoned by vanadium), it is clear 
that, whether the afferent apparatus be affected or not, there is some disorder of the 
other series of organs to which reference was made. 
In order to obtain the necessary data, comparative experiments of the following 
nature were carried on : — The femoral artery of one limb of a frog was ligatured, in 
order to prevent the passage of the vanadium solution, which was injected hypoder- 
mically, to the tissues of the leg. Under these circumstances, in which the nerve- 
trunks and motorial and sensory end-organs were kept from the influence of the poison, 
it was found that as the poison began to take effect no difference in behaviour between 
the two legs could be detected. Up to the same moment the same stimulation applied 
to the skin produced the same amount of motion, and at the same time paralysis of 
motion occurred in both limbs and all over the body. When paralysis was complete, 
and the nerves above and below the point of ligature were tested, the same degree of 
stimulation (practically) w T as needed to excite the muscles of each leg to contraction, 
and on comparison with normal frogs it was seen to be just so much as was required to 
excite the muscles in their case. In the same way no difference was discernible in the 
behaviour of the muscles of the two legs and of healthy frogs. In all cases similar 
degrees of stimulation produced the same amount of contraction. Paralysis was there- 
fore not due to any alteration, in the case of reflex activity, of conducting fibres or 
peripheral organs of either afferent or efferent systems; or, in the case of voluntary 
motion, of conducting fibres, motorial end-organs, or muscular tissue. 
In other comparative experiments two frogs were taken of about the same weight, 
and one of them was poisoned by injecting vanadium solution underneath the skin of the 
back. As soon as paralysis of motion was effected both frogs were decapitated, and the 
cords of each stimulated. The slight differences which were sometimes observed in the 
degree of stimulus needed to induce contraction w 7 ere only such as might be attri- 
MDCCCLXXVI. 4 G 
