66a 



CEREBRAL RESPIRATORY CENTRE. 



into two equal halves, each of which acted on both sides of the diaphragm after the medulla 

 was divided just below the calamus scriptorius. The spinal centres must, therefore, be con- 

 nected with each other in the cord. The spinal respiratory centre can be excited or inhibited 

 reflexlv ( Wrrtheimer). . , , , . - ,, 



Anatomical Schiff locates the respiratory centre near the lateral margins of the grey matter 

 in the floor of the 4th ventricle, but not reaching so far backwards as the ala .cinerea. 

 According to (Jierke, Heidenhain, and Langendorff, those parts of the medulla oblongata whose 

 destruction causes cessation of the respiratory movements are single or double strands of 

 nervous matter, containing grey nervous substance with small ganglion cells and running 

 downwards in the substance of the medulla oblongata. These strands are said to arise partly 

 from the roots of the vagus, trigeminus, spinal accessory, and glossopharyngeal (Meynert), 

 forming connections by means of fibres with the other side, and descending as far downwards 

 as the cervical enlargement of the spinal cord (Goll). According to tins view, this strand 

 represents an inter-central band connecting the spinal cord (the place of origin of the motor 

 respiratory nerves) with the nuclei of the above-named cranial nerves. 



Cerebral Inspiratory Centre. According to Christiani, there is a cerebral 

 inspiratory centre in the optic thalamus in the floor of the 3rd ventricle, which is 



stimulated through the optic and auditory 

 nerves, even after extirpation of the cere- 

 brum and corpora striata ; when it is stimu- 

 lated directly, it deepens and accelerates the 

 inspiratory movements, and may even cause 

 a standstill of the respiration in the inspira- 

 tory phase. This inspiratory centre may be 

 extirpated. After this operation, an expira- 

 tory centre is active in the substance of the 

 anterior pair of the corpora quadrigemina, 

 not far from the aqueduct of Sylvius. Martin 

 and Booker describe a second cerebral in- 

 spiratory centre in the posterior pair of the 

 corpora quadrigemina. These three centres 

 are connected with the centres in the medulla 

 oblongata. 



The respiratory centre consists of two 

 centres, which are in a state of activity alter- 

 nately an inspiratory and an expiratory 

 centre (fig. 467), each one forming the 

 motor central point for the acts of inspira- 

 tion and expiration ( 112). The centre is 

 ins, inspiratory, and cxp, expiratory centre automatic, for, after section of all the sen- 

 motor nerves are in smooth Hues. Ex- S ory nerves which can act reflexly upon the 

 piratory motor nerves to abdominal centrP if *till rpfains its nntivitv Thp Hp- 

 muscles,a6; to muscles of back, do. In- centre > u still retains its activity. Ine de- 

 spiratory motor nerves, ph, phrenic to g ree of excitability and the stimulation of 

 diaphragm, d ; int, intercostal nerves ; the centre depend upon the state of the 

 rl, recurrent laryngeal ; ex, pulmonary blood, and chiefly upon the amount of the 

 fibres of vagus that excite inspiratory blood-cr fl cp thp O nnrl PO ( T Rn^r>fhn/\ 

 centre; car', pulmonarv fibres that excite looa f ases > tne <-' a ^2 (J. Mosenthal). 

 expiratory centre; ex", fibres of sup. Accor ding to the condition of the centre, there 

 laryngeal that excite expiratory centre ; are several well-recognised respiratory con- 

 inh, fibres of sup. laryngeal that inhibit ditions 



the inspiratory centre. L Apncea. -Complete cessation of the 



respiration constitutes apnoea, i.e., cessation of the respiratory movements, owing 

 to the absence of the proper stimulus, due to the blood being saturated with and 

 poor in COg. Such blood saturated with O fails to stimulate the centre, and hence 

 the respiratory muscles are quiescent. This seems to be the condition in the foetus 

 during intrauterine life. If air be vigorously and rapidly forced into the lungs of 

 an animal by artificial respiration, the animal will cease to breathe for a time, after 



Fig. 467. 

 Scheme of the chief respirator}' nerves. 





