342 Dr. W. M. Bayliss. On Reciprocal [Jan. 20, 
paper above referred to. Ostroumoff,* however, in his work on the dilatation 
of cutaneous vessels, had already expressed the view that, in this particular 
case, the action of the depressor nerve is due to an excitation of vaso-dilator 
fibres and not to an inhibition of constrictor tone. Biedl,f at a later date, 
came to the same conclusion with regard to the vascular innervation of the 
adrenals. Cyon,t himself, on the other hand, strenuously opposes this 
interpretation of the facts. None of these observers recognises the possibility 
of both effects being present at the same time. 
(1) Excitation of Dulators—All the vaso-dilator nerves to the posterior 
limbs are contained in the dorsal roots of the sacral plexus.§ All the 
constrictors are situated in the abdominal sympathetic, having left the spinal 
cord in the white rami from the eleventh thoracic to the third lumbar segments 
inclusive] If, then, the spinal cord be transected at the fourth lumbar 
segment the hind-limbs will be, as regards their vaso-motor supply, in 
connection with the central nervous system by means of vaso-constrictor 
fibres only; and, if the abdominal sympathetic chain on both sides be 
extirpated, the dilators alone will be left. When this latter operation has 
been performed, it is found that dilatation of the limbs can still be obtained 
on exciting the depressor nerve. This can only be due to excitation of vaso- 
dilator fibres. The evidence for this statement is given in my paper above- 
mentioned. I will, therefore, merely refer to the experiment shown in fig. 10, 
p. 293, of that paper.{ 
The objection may be made that the dilator impulses to the limbs are of a 
peculiar nature, being antidromic. It is, therefore, important to test the 
behaviour of organs, such as the submaxillary gland, the penis, or the tongue, 
where the dilators are of the recognised type. 
The submaxillary gland suggests itself at once for this purpose, since it is 
easy to observe changes in the venous outflow by inserting a cannula in the 
peripheral end of the external jugular vein, after having tied all branches 
except that from the gland. Hirudin, in doses of about 0-02 gramme per 
kilogramme was found to be sufficient to prevent clotting in the cat. The 
drops of blood were allowed to fall on a slip of mica attached to the end of the 
lever of a Marey tambour, in connection with another tambour which recorded 
each drop on the smoked paper. The cervical sympathetic was cut on both 
sides, so that the gland was supplied with dilator fibres only, conveyed by the 
* © Arch. f. d. ges. Physiol.,’ vol. 12, p. 277, 1876. 
t+ ‘Arch. f. d. ges. Physiol.,’ vol. 67, p. 469, 1897. 
t Article “ Dépresseur (nerf),” Richet, ‘Dictionnaire de Physiologie,’ vol. 4, p. 786, 1900. 
§ Bayliss, ‘Journ. of Physiol.’ vol. 28, p. 276, 1902. 
|| Bayliss and Bradford, ‘Journ. of Physiol.,’ vol. 16, p. 10, 1894. 
q ‘Journ. of Physiol.,’ vol. 28, p. 298, 1902. 
