POSITION OF THE RESPIRATORY CENTRE. 66 1 



9. There is a subordinate centre in the medulla oblongata, which seems to be 

 concerned in bringing the various reflex centres of the cord into relation with each 

 other. Owsjannikow found that, on dividing the medulla 6 mm. above the calamus 

 scriptorius (rabbit), the general reflex movements of the body still occurred, and 

 the anterior and posterior extremities participated in such general movements. If, 

 however, the section was made 1 mm. nearer the calamus, only local partial reflex 

 actions occurred ( 360, III., 4) ; [thus, on stimulating the hind-leg, the fore-legs 

 did not react the transference of the reflex was interfered with]. The centre 

 reaches upwards to slightly above the lowest third of the oblongata. 



The medulla in the frog also contains the general centre for movements from place to place. 

 Section of this region abolishes the power to move from place to place; when external stimuli 

 are applied, there remains only simple reflex movements (Steiner). 



Pathological. The medulla oblongata is sometimes the seat of a typical disease, known as 

 bulbar paralysis, or glosso-pharyngo-labial paralysis {Duchenne, 1860), in which there is a 

 progressive invasion of the different nerve-nuclei (centres) of the cranial nerves which arise 

 within the medulla, these centres being the motor portions of an important reflex apparatus. 

 Usually, the disease begins with paralysis of the tongue, accompanied by fibrillar contractions, 

 whereby speech, formation of the food into a bolus, and swallowing are interfered with ( 354). 

 The secretion of thick, viscid saliva points to the impossibility of secreting a thin watery facial 

 saliva ( 145, A), owing to paralysis of this nerve-nucleus. Swallowing may be impossible, 

 owing to paralysis of the pharynx and palate. This interferes with the formation of consonants 

 [especially the Unguals, I, t, s, r, and, by and by, the labial explosives b, p] ( 318, C) ; the 

 speech becomes nasal, while fluids and solid food often pass into the nose. Then follows 

 paralysis of the branches of the facial to the lips, and there is a characteristic expression of the 

 mouth "as if it were frozen." All the muscles of the face may be paralysed ; sometimes the 

 laryngeal muscles are paralysed, leading to loss of voice and the entrance of food into the 

 windpipe. The heart-beats are often retarded, pointing to stimulation of the cardio-inhibitory 

 fibres (arising from the accessorius). Attacks of dyspncea, like those following paralysis of the 

 recurrent nerves ( 313, II., 1, and 352, 5, b), and death may occur. Paralysis of the muscles 

 of mastication, contraction of the pupil, and paralysis of the abducens are rare. [This disease 

 is always bilateral, and it is important to note that it affects the nuclei of those muscles that 

 guard the orifices of the mouth, including the tongue, the posterior nares including the soft 

 palate, and the rima glottidis with the vocal cords. ] 



368. RESPIRATORY CENTRE. INNERVATION OF THE RESPIRA- 

 TORY ORGANS. The respiratory centre lies in the medulla oblongata (Legallois, 

 1811), behind the superficial origin of the vagi, on both sides of the posterior 

 aspect of the apex of the calamus scriptorius, between the nuclei of the vagus and 

 accessorius, and was named by Flourens the vital point, or nceud vital. The centre 

 is double, one for each side, and it may be separated by means of a longitudinal 

 incision (Longet, 1847), whereby the respiratory movements continue symmetrically 

 on both sides. Section of Vagi. If one vagus be divided, respiration on that 

 side is slowed. If both vagi be divided, the respirations become much slower and 

 deeper, but the respiratory movements are symmetrical on both sides. Stimulation 

 of the central end of one vagus, both being divided, causes an arrest of the 

 respiration only on the same side, the other side continues to breathe. The same 

 result is obtained by stimulation of the trigeminus on one side (Langendorff). When 

 the centre is divided transversely on one side, the respiratory movements on the 

 same side cease (Schiff). Most probably the dominating respiratory centre lies 

 in the medulla oblongata, and upon it depend the rhythm and symmetry of the 

 respiratory movements ; but, in addition, other and subordinate centres are placed in 

 the spinal cord, and these are governed by the oblongata centre. If the spinal cord 

 be divided in newly-born animals (dog, cat) below the medulla oblongata, respira- 

 tory movements of the thorax are sometimes observed (Bracket, 1835). 



[If the cord be divided below the medulla, or the cranial arteries ligatured (rabbit), there 

 may still be respiratory movements, which become more distinct if strychnin be previously 

 administered, so that Langendorff assumes the existence of a spinal respiratory centre, which 

 he finds is also influenced by reflex stimulation of sensory nerves.] 



Nitschmann, by means of a vertical incision into the cervical cord, divided the spinal centre 



