554 MR. J. PRIESTLEY ON THE PHYSIOLOGICAL ACTION OP VANADIUM. 
butable to the defect of aeration in the poisoned frog due to the early cessation of respira- 
tion. Paralysis was therefore not due to any defect of conducting-power in the cord. 
The preceding results were verified, as far as was possible, in the case of young 
mammals. 
The cause of paralysis, therefore, presumably affects the initial cells concerned in the 
origination or transmission of nervous impressions. 
The experiments on the reflex activity of frogs, both with and without the presence 
of brain (and Setchenw’s inhibitory centres in the optic lobes), show a diminution of 
irritability, which must be attributed to centric disturbance, since afferent and efferent 
nerves are unaffected. 
It is only necessary to allude here to the action of vanadium upon the special centres 
of the cord. It acts upon the vasomotor centre in such a manner as, in course of time, 
to release the arterial tonus, and it first excites, and afterwards depresses, the respiratory 
centre, as is shown in figs. 5 & 6, Plate 46. It may be noticed that the effects of poisoning 
by vanadium do not increase with regularity. In the case of the reflex, as of the circu- 
latory and respiratory centres, there occur brief, but very well-marked, periods during 
which functional activity is almost fully resumed before finally succumbing to the 
poison. This is well shown in figs. 1, 2, 5, & 6, Plates 45 & 46. 
With regard to sensibility, no indications were noticed of any defect, either in the 
experiments on the general effects of poisoning or in the comparative experiments 
mentioned above. 
No cerebral symptoms were seen, except the sluggishness which occurred in all cases 
of poisoning; and in other respects the animals experimented upon (except frogs, in 
which the occurrence of general paralysis rendered it impossible to judge) remained 
apparently conscious until death. 
Special experiments were undertaken to discover whether vanadium (an intense 
irritant poison) was not also a muscle-poison. No indications of its being a muscle- 
poison could be detected. (See figs. 3 & 4, Plates 45 & 46.) 
IY. CONCLUSION. 
Prom the experiments and observations described in this paper it results : — 
1. That vanadium is a metal possessed of intense poisonous activity. 
2. That it manifests this poisonous activity when a soluble salt (a vanadate) is intro- 
duced into the system by the stomach, by subcutaneous injection, or by direct 
injection into veins. 
3 That it interferes with the vital functions of simple organisms. 
4. That it destroys the irritability of muscular and nervous tissues when directly 
applied to them, even in very dilute solutions. 
5. That when introduced into the system by the stomach, or subcutaneously, it 
produces congestive and inflammatory changes in the alimentary mucous 
membranes. 
6. That it exerts no direct action on the blood. 
