540 MR. J. PRIESTLEY ON THE PHYSIOLOGICAL ACTION OP VANADIUM. 
the symptoms is reached, after which the characters of respiration again become normal. 
Respiration then declines until death, the decline being gradual in some cases, but 
marked in others by periods of increased 'vigour and frequency. Death seems to be 
proximately caused by failure in respiration. There are, therefore, (1) a stimulation 
and (2) a depression of respiration, which may result either from some lesion of the 
respiratory centre in the medulla, or from some affection of the afferent respiratory 
nerve — the vagus. As the usual respiratory symptoms seem to follow after section of 
both nervi vagi, we must assume the disturbance of respiration caused by vanadium to 
be centric. 
V. SPECIAL ACTION OF THE POISON ON THE FUNCTIONS OF THE MUSCULAR AND 
NERVOUS SYSTEMS. 
In the following experiments frogs were the animals chiefly used, the common Bana 
temporaria being caught from time to time in the neighbouring ponds for the purpose. 
The minimum stimulus required to produce movement in a muscle was the test made 
use of. A Du Bois-Reymond’s induction-machine was used in stimulation, the coils 
being gradually approximated until the feeblest contraction occurred, and the distance 
between them then noted. Interrupted currents were generally used, but single induc- 
tion-shocks were sometimes resorted to. 
The next seven experiments were devised to show the action of vanadium upon the 
motor and sensory powers of the nervous system and upon muscles. 
Exp. LXI.— May 19, 1874. 
h. m. 
1 45. 
1 50. 
1 52. 
2 23. 
2 30. 
30 . 
Frog. — Weight 25 gratis. 
Dose 1 cub. centim. of the 5 per cent, solution (5 milligrammes V 2 0 5 ), 
injected under the skin. 
The femoral artery of right leg exposed and ligatured a little way above the 
middle of the thigh. Injection complete; lively; jumps about. 
Lies down, with ligatured leg spread out. 
Drags ligatured limb. 
Lies quiet ; moves spontaneously. 
Both legs lie spread out. On touching the ligatured leg the frog kicked twice 
with the other. 
On pinching the non-ligatured leg both legs were moved, but not so 
vigorously as before. 
On pinching the right arm both legs moved, but the ligatured one first. 
Quite dead. Rigor mortis appears to have commenced. 
Exposed the sciatics of both legs quickly. 
1 Leclanche’s element. Interrupted currents. 
