1908. | Innervation in Vaso-motor Reflexes, etc. 357 
strictors, as usually stated. Accordingly, I find that this drug, injected 
subsequently to a dose of strychnine, causes a fall of pressure, just as a 
second dose of strychnine itself would have done. On the other hand, 
bodies acting peripherally, like adrenaline, still produce a rise after 
strychnine, apparently as great as normally. 
Vascular Reflexes under Strychnine. 
The effect of a small dose is to increase general excitability, not only as 
regards pressor, but also depressor, reflexes. Fig. 14 is an interesting case of 
this. In my work on the causes of the depressor fall of arterial pressure, 
I was never able to obtain a dilatation of the renal vessels of sufficient 
magnitude to counteract the effect of the fall 
of blood-pressure so as to produce an actual 
increase of volume of the organ. In the ex- 
periment of which the tracing of fig. 14 forms 
a part, a similar passive diminution in renal 
volume was seen on depressor excitation at 
the beginning. After injection of 0:013 gramme 
of strychnine, the depressor gave rise to an 
actual increase of volume. As will be seen later, 
this dilatation is probably due to excitation of 
dilators, rather than to increased excitability eae 
to inhibitory influences. 
Bie 
As the dose is progressively increased, the 
Fie. 14.—Effect of the depressor 
mmerve on the kidney after a 
dose, a change in its effect on the arterial small dose of strychnine. 
pressure is seen to make its appearance, step § Upper curve, volume of kid- 
by step. The first sign of this change is that °°” Pas ak cil dia cua 
the fall of pressure is of short duration only sie Oral 
and is followed by a slight rise, which becomes, as the dose is increased, 
greater in relation to the fall, until it alone is left and finally itself disappears, 
owing to abolition of all reflex excitability. Fig. 15 gives a series of such 
curves from the rabbit. 
It was necessary in this case to inject 7 centigrammes of the sulphate, in 
order to produce complete conversion of the fall into a rise. This would be 
a colossal dose for man, but the rabbit is very insensitive to strychnine. In 
depressor nerve being excited between each 
eats and dogs the effect is brought about by a fifth of this dose. Individual 
animals, of each species, vary as to the dose required; probably age is the 
factor concerned. 
Although there can be no reasonable doubt that the cause of the rise of 
2F 2 
