444 PHYSIOLOGY CHAP. 



must be recapitulated in its principal headings. Galen already 

 knew that a section through the highest part of the cord produced 

 the immediate death of the animal. " Perspicuum est, quod si 

 post primam aut secundam vertebram, aut in ipso spinalis medullae 

 principio sectionem ducas, repente animal corrumpitur" (De 

 anat. administr. lib. viii. cap. ix.). 



This experiment was successfully repeated in 1760 by Lorry, 

 arid perfected in 1811 by Legallois, who at a later time showed 

 experimentally on the rabbit that " respiration depends upon a 

 very circumscribed region of the medulla oblongata, which is 

 situated at a short distance from the occipital sulcus, and near the 

 origin of the eighth or pneumo-gastric nerves." 



A few years later (1842) Flourens took up these experiments 

 of Legallois, and endeavoured to localise the respiratory centre 

 more exactly, but he added nothing substantial to the results of 

 Legallois. In a subsequent communication (1851) he defined as 

 point, ou nceud vital a very minute tract of grey matter, the size 

 of a pin's head, lying in the median line towards the tip of the 

 calamus scriptorius, ablation of which infallibly led to the 

 immediate death of the animal. 



It was, however, shown by Volkniann (1842), Longet (1847), 

 and M. Schiff (1858) that the respiratory centre is a double 

 organ, which can be divided by a median longitudinal section 

 down the sinus rhomboidalis into two halves, without causing 

 arrest of respiration by the section. After these publications 

 Flourens also (1859) recognised that the nceud vital is double, 

 and that in order to destroy life " a transverse section of 5 mm. is 

 required, passing through the centre of the V. of grey matter in 

 the medulla oblongata," i.e. half way up the beak of the calamus 

 scriptorius. 



Longet, and even more definitely Schiff, endeavoured to show 

 that the true respiratory centre is located in the large nucleus of 

 grey matter in the alae cinereae, which lies in the lower part of 

 the bulb, external to the nucleus of the hypoglossus, beneath the 

 floor of the fourth ventricle, and that the paths by which the 

 impulse is conducted thence to the spinal cord run in the lateral 

 bundles, unilateral section of which, at the lower level of the bulb, 

 or at the level of the second and third cervical vertebrae, suffices 

 to produce respiratory paralysis of the muscles of the same side 

 (Schiffs respiratory hemiplegia). The animal may survive this 

 operation for weeks and months, and active movements of 

 respiration never reappear on the operated side (1854). 



This last fact suffices to refute Brown-Sequard, who in 1858 

 denied the existence of a bulbar respiratory centre. In his opinion, 

 the sudden death of the animal after lesion of the bulb was the 

 effect, not of paralysis or deficiency, but of traumatic excitation of 

 an inhibitory centre or the paths for the respiratory movements. 



