The Purvis Oration ON RESPIRATORY PHENOMENA IN NERVOUS DISEASE: Delivered before the West Kent Medico-Chirurgical Society on December 9th, 1921
Authors: J. P. Stewart
Journal: BMJ (1921)

A-PART-froln the large proportion of our patients who suffer from primary respiratory affections, there are a considerable number who exlhibit respiratory symptoms which are a consequence or complication of other maladies.I wish, here-to draw attention to that important group wnich we find occurring secondary to various diseases of the nervous system. .sytem.;.VRespiratory Centres.Let me fil-st of all recall.the nervous mechanism of respiration.The primary or lowest reflex respiratory centre -is located in the lower part of the medulla cblongata,: probably in the region of the visceral sensory nucleus -of tlhe fasciculus solitarius.Tllis vital centre maintains ordinary breathing witli its regular rhythm.During ordinary quiet breathing the inspiratory phase is an active mnuscular process of sucking air into the lunas; ekpiration, on the other hancd, is a mere passive recoil of thle lungs and.thoracic cage, due to elasticity of their tissues.Th1e muscles involved in ordinary inspiration comprise, fn-st, the diaphragm (innervated by the phrenic nerves whose motor nucleus in the spinal cord is at the level of the third, fourtlh, and fiftlh cervical segments); and second, -tlle -intercostal muscles (innervated by the series of anterior spinal roots from the first to the twelfth thoracic inclusive).Durirg forced or laboured respiration, and also in cbuglhing and sneezing, various supplementary or acces- sory muscles, both inspiratory and expiratory, are called in, so as to reinforce the ordinary mechanism of inspiration and, recoil.Ordinareily the respiratory centre in the medulla is e@cited to activity by variations in the oxygen and carbon dioxide content of the blood.But it is also influenced by nervou s--stimuli.These stimuli reach it through various senory nerves, clhiefly along the vague, which is the visce-al sensory nerve of the respiratory tract, but also from almost any sensory nerve of tlle body; thus coughing aid.other respiratory reflexes can be induced by widely -Pcieda above the vital respiratory centre in the medulla there a hiigher reflex centre in the mid-brain, situated b!ilaterally in the mesial part of the optic thalami.This centre is concerned with emotional reflexes, such as laughing and sobbing, actions which involve modifications of the respiratory movements, accompanied at times by secretory pheiotnena,-suchl as lacrymation, and even by visceral phenomena,-for example, precipitate contractions of the bladder or bowel.Lastly, higher still, there are motor centres in thie: cerebral cortex, by means of which we can exereise Xa partial vohmntary conrol over tlle loyver respiratory mechanismns.It is not surprising -that these complex respiratory centres, situated as they are deep within the brain,.medulla, and spinal cord, are liable to beconie disordered in diseases and injuries of the nervous system, whetlher thle lesion implicates tlhe-central n6rvous system itself or thsi.;ensory or mnotor elements of the reflex respira- tory *C.-Ietsirato-y pllenom-ena are coMmonly an accessor;y.element in nervous diseases or injuries; somretirnes, llowever, they may dominate, for a time, the hliole clinical picture.