1908. | Innervation in Vaso-motor Reflexes, etc. 341 
to, it is necessary to be able to make use of organs which are supplied with 
both vaso-constrictor and vaso-dilator nerves, and these two kinds of fibres 
must pass to the organ in anatomically distinct nerve-trunks. When this is 
the case, it is possible to decide by section of one or the other whether a 
particular result is due to one of these alone. For instance, if we observe 
a vascular dilatation in the sub-maxillary gland in response to excitation of 
the central end of the depressor nerve, we can decide by section of the 
cervical sympathetic nerve whether the effect is still present. If so, 1t cannot 
be due to inhibition of constrictors alone, there must be also excitation of 
dilators in the Chorda tympani nerve. 
There are, unfortunately, very few organs, accessible to investigation, 
which satisfy these conditions. Such are the sub-maxillary gland, the tongue, 
the external ear in the rabbit, the penis in the dog and the limbs. On all of 
these organs I have made observations. 
General Methods——All animals used were anesthetised with A.C.E. mixture 
and morphine, except in the case of rabbits, where ether was used instead of 
A.C.E. mixture for reasons which will be seen later. With the exception of 
the submaxillary gland, all the organs investigated were placed in oncometers 
of appropriate form and the changes of volume recorded by a piston-recorder. 
In the plethysmographic experiments curare was usually fouud to be 
necessary. The arterial blood-pressure was always traced simultaneously with 
the plethysmographic curve. 
Il. RecipRocAL INNERVATION IN THE NORMAL ANIMAL. 
There are, in the investigation of this question, four cases to be considered. 
In a reflex producing fall of blood-pressure with general dilatation of arterioles, 
is there evidence of both excitation of -vaso-dilator nerves and inhibition of 
central vaso-constrictor tone? In a reflex of the opposite kind, is there 
evidence of both excitation of vaso-constrictor nerves and inhibition of central 
vaso-dilator tone ? 
1. Depressor Reflexes. 
These are to be obtained, as is well known, by excitation of the central end 
of the depressor nerve in the rabbit, also from the central end of the vagus in 
the cat, and, under certain conditions, not exactly definable, from the central 
end of the vagus in the dog. 
The discoverers of the depressor nerve, Ludwig and Cyon, apparently 
regarded its action as purely inhibitory on the vaso-constrictor centre.* This 
was also the usual opinion of subsequent workers until the publication of my 
* * Ber, d. k. Sachs Ges.,’ Math. phys. Classe, vol. 18, p. 318, 1866. 
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