19 Tarchanoff, Pflüger's Arch., viii. p. 97; Ross, Diseases of the Nervous System, vol. i. p. 225.
While these medullary centres are certainly influenced by impulses reaching them from the cerebral hemispheres, as is evident from the vaso-motor symptoms produced by mental action—e.g. pallor from fright, blushing, etc.—it is impossible to state in what portion of the hemispheres in man the higher vaso-motor centres lie. Eulenburg and Landois locate them in the motor area in animals.20 They are certainly beyond control of the will, and are wholly reflex in their action, a purely mental act in this case being the excitant of a purely physical result.21
20 Arch. f. Path. Anat., Bd. lxviii. p. 245.
21 In addition to the articles already cited the reader is referred to Landois's Physiology, to Duval's article, “Vaso-moteurs,” in the Dictionnaire de Médecine et de Chirurgie, vol. xxxviii. (1885), for a summary of vaso-motor physiology, and to Gerhardt's “Ueber Angio-neurosen,” Volkmann's Sammlung klin. Vorträge, No. 209. Gaskell's researches, published in the Journal of Physiology, are the most recent and satisfactory.
PATHOGENESIS.—From this review of the physiology of the vaso-motor system it becomes evident that disturbances of vascular tone may be produced by many different causes acting upon many various parts. They may be due to local affections of the part in which the symptoms are present, as in the case of erythema22 after burns or frost-bite, or congestion of any organ after injury. They may be due to affections of the vaso-motor nerves passing to the part affected, as in the case of vascular changes due to peripheral nerve lesions.23 They may be due to affections of the sympathetic ganglia connected with the part affected, as in the case of migraine,24 sudden flushing of one ear, certain cases of polyuria,25 and Basedow's disease.26 They may be due to lesions in the spinal cord affecting the vaso-motor centres27 or compressing the nerve-roots on their way to and from the sympathetic ganglia,28 as is the case in the various forms of myelitis and in Raynaud's disease or symmetrical gangrene, and in meningitis, tumors of the cord, or Pott's disease. They may also be caused by such conditions in the cord as cut off the vaso-motor centres from the medullary centres, such as transverse myelitis from compression or traumatism.29 They may be due to lesions of the medulla oblongata,30 as is seen in some cases of polyuria and glycosuria,31 and in cases of universal erythema32 following acute fevers. They may be due to diseases of the cerebral hemispheres, as is evident from the vaso-motor symptoms occurring in hemiplegia and hysteria. Finally, they may be of a reflex origin, dependent upon some obscure source of irritation in a part quite distant from the region in which the symptoms appear.33
22 Vol. IV. p. 511.
23 Vol. V., “Neuritis.”
24 Vol. V., “Migraine.”
25 Vol. IV., “Polyuria.”
26 Vol. III. p. 761.