690 



PRINCIPLES OF GENERAL PHYSIOLOGY 



The coronary arteries of the heart are probably in a similar position. But 

 here there appears to be no need for constrictors, since the heart is always at 

 work, and increased supply is automatically provided by rise of aortic pressure 

 and by the great sensibility of the coronary vessels to the metabolites produced 

 by the heart in contraction. 



For some time the supply of vaso-constrictors to the lungs was in doubt. 

 Bradford and Dean described their presence, Brodie and Dixon denied it. 

 Fiihner and Starling (1913) finally proved it by the action of adrenaline. 



Space does not permit of details of the anatomical origin of the various supplies 

 to individual organs. These will be found in my article (1906, 3), and in the 

 papers quoted there. The vaso constrictors are all contained in the sympathetic 



outflow, as described by 

 Gaskell. The vaso-dilators 

 have a more varied origin, 

 especially from cranial and 

 sacral automatic systems. 

 Whether the sympathetic 

 proper contains any vaso- 

 dilator fibres is somewhat 

 doubtful. Reference has 

 been made (page 428) to the 

 possibility of reversal of con- 

 striction under the action of 

 drug?, etc. 



The remarkable nature of 

 the vaso-dilator supply to the 

 limbs, skin of the trunk, and, 

 probably, of the ears and 

 face, and of the intestine 

 requires mention. Strieker 

 had described vascular dilata- 

 tion in the foot of a dog 

 when he stimulated the peri- 

 pheral ends of dorsal roots 

 in the sacral region, but the 

 statement was not generally 

 accepted until my work 

 (1901, 2), on account of the 

 apparent contradiction of the 

 law of Bell and Magendie 

 (Fig. 237). I showed that 

 the fibres concerned have 

 anatomical relationships 

 similar to those of the 

 ordinary sensory fibres, and 



appear to be identical with them. I suggested that there might be a peri- 

 pheral nerve network around the arterioles, common to both sensory fibres 

 and vaso-dilator nerves. This view was confirmed by the work of Ninian Bruce 

 (1910). Starting from the fact that paralysis of sensory nerves by cocaine prevents 

 the application of oil of mustard from causing inflammation, he showed that 

 the inflammation produced by this irritant is due to an axone reflex to the 

 arterioles. It is unaffected by mere section of the nerve trunk, but disappears 

 if the nerve fibres are allowed to degenerate. Thus a sensory fibre has a vaso- 

 dilator branch to an arteriole, and, when the receptor organ is stimulated, the 

 nerve impulse, as it reaches the branch, passes along it and causes dilatation of 

 the arteriole (see the diagram of Fig. 145, page 474). It will be noted how the 

 four classical characteristics of inflammation heat, pain, redness, and swelling 

 fit in with this view : pain from the sensory component, heat, redness, and 

 swelling from the vascular dilatation. I found also (1902, 3) that stimulation of 



FIG. 237. VASO-DILATATION IN THE LEG ON STIMULATION 

 OF THE FIRST SACRAL DORSAL ROOT. Nine da vs after 

 removal of the spinal cord from the second lumbar 

 segment downwards, leaving intact the dorsal root 

 ganglia. The ventral roots were completely degener- 

 ated and inexcitable. 



Upper tracing, blood pressure. 



Lower tracing, volume of the hind leg. 



The upper, straight line is the zero of the blood pressure. 



The lower, signal line marks the duration of stimulation. 



(Bayliss, 1901, 2, p. 191.) 



