56 The Encephalon 



sneezing, and hiccough.' The efferent impulse leaves by the phrenic, 

 intercostals, spinal accessory, certain cervical nerves, and facial. Vaso- 

 motor centre, controlling the muscular coat of the large arteries of the 

 thorax, abdomen, and pelvis, through efferent impulses carried down 

 by the spinal cord, the dorsal nerves, and the'splanchnics. Dilatation 

 of these vessels follows section of the cord below the medulla. Cardio- 

 inhibitory, through which the heart is held under control by afferent 

 influences passing to the medulla, acceleration of the heart's action 

 following section of the vagus. The medulla contains also a centre 

 for deglutition, and one which, being stimulated, produces glycosuria 

 the diabetic centre and a salivary centre. Sugar and albumen may 

 be found in the urine in the case of lesion of the medulla. 



Bulbar paralysis is the result of progressive degenerative changes 

 in the nuclei of origin of the hypoglossal, spinal accessory, vagus, 

 facial, and glosso-pharyngeal, which are near neighbours in the floor 

 of the fourth ventricle. The co-ordination of muscles of articulate 

 speech become gradually implicated, and the tongue and the muscles 

 of the pharynx lose their power. The disease used to be called labio- 

 glosso-pharyngeal paralysis ; the term bulbar paralysis is shorter, and 

 moreover indicates the seat of the primary lesion, in the ' bulbar ' end 

 of the spinal cord (see p. 71). 



The aqueduct of Sylvius leads beneath the corpora quadrigemina 

 and posterior commissure from the top of the fourth ventricle into the 

 third. It is lined by a prolongation of the grey matter from the 

 fourth ventricle, in which are the nuclei of origin of the motor oculi 

 and patheticus. 



When the basal ganglia are in physiological activity the vessels, 

 which enter them in great abundance, are filled full, and the ganglia 

 are increased in size. The corpora striata in their turgescence bulge 

 into the lateral ventricles, displacing some of the intra- ventricular fluid 

 which is secreted by the choroid plexuses, through the foramina of 

 Monro, into the third ventricle ; and the thalami, growing large, 

 squeeze fluid out of that ventricle through the aqueduct and into the 

 fourth ventricle, and so into the subarachnoid space. As an infant 

 with spina bifida excites himself, and cries, the brain evidently in- 

 creases in bulk, for the lumbar tumour becomes tense and swells up. 

 And as the brain quiets down again the cerebro-spinal fluid re-enters 

 the cranium, some of it, no doubt, passing into the third and lateral 

 ventricles by the apertures of Sylvius and Monro. In cases of dilatation 

 of the third lateral ventricles (internal hydrocephalus] Hilton 1 found 

 that the communication between the ventricles and the subarachnoid 

 space was permanently blocked, so that the intra-cerebral fluid could 

 not escape. Sometimes the brain-tissue is represented by but a thin, 

 smooth film enclosing the 'water,' which has sometimes measured,/^/ 

 mortem, twelve or twenty pints. In such cases the head may appear 



1 Rest and Pain, 2nd edit. p. 28. 



