REGULATING THE CONTRACTIONS OF THE ARTERIES 47 
It was observed by Wharton Jones,’ that section of the sciatic nerve in 
the thigh of a frog was followed after a time by oedema of the limb and ex- 
foliation of the epidermis. If this were dependent on the dilatation of the 
arteries produced by the division of the nerve, the fact would have a very 
important bearing upon the cause of inflammatory effusion. I find, however, 
that neither oedema nor exfoliation results from permanent full dilatation 
produced by operations upon the cord or the roots of the spinal nerves ;_ while, 
on the contrary, both took place in the case of division of the sciatic, given in 
the early part of this paper, in which it will be remembered that the arteries 
recovered their contractility completely within half an hour, and presented, 
during the next twenty-four hours, precisely similar appearances with those 
in the other foot. Hence it is evident that the phenomena in question are not 
due to vascular relaxation, but to some other circumstances attending the 
operation performed upon the thigh. 
It remains to be added, that, in a healthy state of the web, no change 
in the properties of the blood was ever observed to accompany the constriction 
of the arteries on irritation of the cord, or the dilatation which followed the 
destruction of the nervous centre. The exsanguine condition of the web in the 
former case, and the turgid state of the vessels in the latter, were simply the 
effects of the variations of calibre in the arteries, the blood flowing more freely 
in proportion to their width.” 
To sum up the principal results of this inquiry, it appears— 
ist. That, of the nervous centres usually recognized, the cerebro-spinal 
axis 1s the only part which regulates the contractions of the arteries of the webs ; 
this function being apparently exercised by the whole length of the cord and 
the posterior part of the brain, operating through fibres which arise from the 
same region of the cord as do those through which sensation and motion are 
effected in the hind legs. 
2nd. That there exists within the hmb some means, probably ganglionic, by 
virtue of which the fibre-cells of the circular coat of the arteries may contract in 
concert with each other, independently of any ganglia contained in the trunk. 
And 3rd, that the local co-ordinating apparatus, though capable of indepen- 
dent action in special conditions of direct irritation, is, under ordinary circum- 
stances, in strict subordination to the spinal system; while a remarkable 
provision exists for the maintenance of this control, notwithstanding almost 
complete severance of nervous connexion between the cord and the limb. 
1 Medico-Chir. Trans., loc. cit. 
* The subject of the effect of variations in the calibre of the arteries upon the flow through the 
capillaries, will be found fully discussed in the paper ‘On the Early Stages of Inflammation’ (reprinted 
in this volume, p. 200). 
