534 ME. J. PEIESTLEY ON THE PHYSIOLOGICAL ACTION OF VANADIUM. 
circulation is threefold. In the first place, there is a diminution of blood-pressure, 
which, however, is not quite continuous, but is marked by intervals in which there is 
a tendency to regain the former height ; these alternate rises and falls take place with 
considerable regularity. In the second place, there is a disappearance of respiration- 
curves ; and in the third place, there is irregularity and diminution in rapidity of the 
pulse, which, like the fall of blood-pressure, is not quite regular. In the case of. injec- 
tion into veins there was scarcely time, owing to the rapidity of death, for the develop- 
ment of the marked fluctuations noticed when injection was hypodermic. 
The disappearance of respiration-curves can only be due to some alteration of the 
vasomotor centre, whose oscillations of activity are the cause of them. The marked 
fall of blood-pressure might be due to one or more of the following circumstances : — 
1, paralysis of the vasomotor centre ; 2, peripheral irritation of depressor nerves ; 3, 
relaxation of arterial tonus due to other causes than vasomotor paralysis ; 4, weakening 
of the heart’s action. The alteration of the pulse may be caused by 1, some action 
•upon the vagi ; 2, poisoning of intracardiac centres ; 3, poisoning of muscular substance 
of heart ; 4, diminution of blood-pressure. As previous division of the vagi does not 
seem in the least to alter the circulatory effects of poisoning by vanadium (Experiments 
XLVIII. & XLIX.), it is clear that none of these effects can be attributed to an action 
on the vagi. It is, moreover, evident, from experiments detailed elsewhere in this 
paper, that there is no poisoning of the muscular substance of the heart itself. Further, 
the fact that vanadium does not paralyze unstriped muscles in other regions of the body 
(as in the intestines) renders it probable that there is no direct action upon the muscular 
walls of the arteries. We may therefore at once eliminate both these possibilities 
from the question. It will be seen on comparison that the fluctuations in blood- 
pressure and in pulse are only sometimes coincident ; neither will, therefore, serve as 
sufficient explanation of the other, although the effects may be partially due to their 
interaction. There remains, therefore, the vasomotor system of nerves, with the 
depressors and the intracardiac nervous mechanism, to which we must look for the 
chief explanation of the phenomena under consideration. From the experiments in 
which the cord was divided in the neck, we gather that the effects of vanadium-poisoning 
upon the pulse occurred as usual, while the diminution and fluctuations in blood- 
pressure were no longer visible, being indeed replaced by a rise. As in those experi- 
ments the vasomotor centre, the accelerators, and the vagus centre and terminations 
were eliminated (the vagus terminations by means of the curare which was injected), we are 
driven to the conclusion (1) that the depression and fluctuations of blood-pressure are for 
the most part due to some action of the poison on the vasomotor centre, and (2) that the 
irregularities of heart-beats are caused by an affection of intracardiac ganglia. The 
former conclusion is strongly confirmed by the disappearance of respiration-curves, which 
must be due to vasomotor mischief, and by the fact that other centres in the cord are 
acted on by vanadium. Hence it seemed hardly necessary to perform any special experi- 
ments after elimination of the depressors. The latter conclusion is fully borne out by 
