286 MECHANISM OF THE RESPIRATORY MOVEMENTS. 



outside and below the nucleus of the pneumogastric and glosso- 

 pharyngeal nerves. It is surrounded by gelatinous grey matter with 

 many small nerve cells. " Its fibres appear to lose themselves among 

 the cells of the enclosing grey matter, and this and the bundle gradually 

 disappear when traced towards the spinal cord. Traced upwards, the)' 

 pass out with the bundles of nerve-roots which go to form the vagus 

 and glosso-pharyngeal." 1 



Mislawsky, 2 who experimented on cats, concluded that the respira- 

 tory centre was to be found, not in Gierke's bundle, but in two cell 

 groups lying in the formatio reticularis on each side of the median raphe 

 internal to the roots of the hypoglossal nuclei. The latest attempts to 

 localise the centre have been made by Gad and Marinesco. 3 In order to 

 destroy the medulla oblongata bit by bit, these observers used minute hot 

 glass beads, the destructive action of which could be accurately 

 localised. In this way they claim to have burnt away the whole of the 

 medulla oblongata corresponding to the situations laid down by Flourens, 

 Gierke, and Mislawsky for the respiratory centre, without altering the 

 respiratory movements. They themselves locate the centre in the cells 

 of the formatio reticularis, and consider that it occupies an extensive 

 area in this formation on each side of the middle line ; it certainly 

 cannot be restricted to a part the size of a pin's head, as was supposed 

 by Flourens. 



Although the evidence in favour of the localisation of the respiratory 

 centre in the medulla oblongata is apparently so convincing, certain 

 observers have denied altogether the adequacy of the experiments 

 adduced in its support. Thus Brown-Sequard, 4 in 1860, showed that, if 

 young animals were kept alive by artificial respiration for some time 

 after the division of the cord below the medulla oblongata, on ceasing the 

 artificial respiration co-ordinated movements of thorax and diaphragm 

 might still for a time be observed. He considered therefore that the centre 

 of respiration was not confined to a circumscribed area in the medulla 

 oblongata, but extended throughout the spinal cord. The effects on 

 respiration which follow section of the cord below the medulla oblongata, 

 he ascribed to inhibition of these spinal centres consequent on the 

 lesion acting as a stimulus, and compared the result to the phenomena 

 accompanying shock. Twenty years later this idea was warmly taken 

 up by Langendorff, 5 who carried out a number of experiments similar to 

 those of Brown-Sequard, in order to prove the independent automatism 

 of the spinal centres. Wertheimer 6 also pointed out that if an adult 

 animal (dog) were kept alive by means of artificial respiration for some 

 hours after section of the cervical cord, rhythmic respiratory movements 

 of the thorax take place as soon as the artificial respiration is dis- 

 continued ; he states that in one case a dog survived the cessation of 

 artificial respiration about three-quarters of an hour, respiration all this 

 time being carried out by the spinal centres. These experiments have 

 been repeated by a number of other observers, who, while confirming to 

 a certain extent the previous results, were unable to attribute to them 

 the same importance. As I have already pointed out, the cells from 



1 Schiifer in " Quain's Anatomy," vol. iii. part 1, p. 55. 



2 Centralbl. f. d. med. Wissensch., Berlin, 1885, S. 465. 



3 Arch. f. Physiol., Leipzig, 1893, S. 175. 



4 Journ. de la physiol. de I'homme, Paris, 1860, tome ii. p. 153. 



5 Arch./. Physio/., Leipzig, 1880, S. 518 ; ibid,, 1887, S. 237 ; ibid., 18S8, S. 283. 



6 Journ. de Vanat. et physiol., etc., Paris, 1886, tome xxvi. p. 458. 



