352 Dr. W. M. Bayliss. On Reciprocal [Jan. 20, 
cord itself transected immediately below the lowest root cut. It was found, 
post mortem, that the roots from the third to the seventh lumbar inclusive 
had been divided, and the cord was completely severed with the exception of 
a small piece of the anterior columns. The central end of the sixth root was 
prepared for excitation. The left hind-leg was placed in a plethysmograph. 
At first excitation of the central end of the dorsal root produced the usual 
pressor effect, a reflex constriction of the lmb, precisely similar to that 
resulting from the median nerve, so that the Lovén effect appeared to be 
absent. On carefully raising the root well away from the tissues, however, 
a different result was obtained. With the same strength of exciting current 
the rise of blood-pressure was less, a fact indicating escape to the posterior 
columns of the cord in the previous case, while in the leg, instead of con- 
striction, there was now well-marked dilatation. Fig. 8 shows the contrast 
between the effect of the median and that of a dorsal root carrying sensory 
ait Ni 
iy | 
Hy! Wi) “na iH iN Aa 
Fic. 8.—Inhibition of constrictors in Lovén reflex. Upper curves, volume of hind-limb. 
Lower curves, arterial pressure. Zero, 35 mm. below line of excitation- 
marker. First excitation, median nerve. Second ditto, central end of 
sixth lumbar dorsal root. 
impulses from the limb itself. Since the dilators were cut, the effect was due 
to inhibition of constrictors. We see, then, that reciprocal innervation holds 
in the case of Lovén, or local, reflexes. 
The question was also investigated on the tongue. Excitation of the central 
