Sensory and Motor Tracts in Encephalon. 15 



pairs, and finally in the cervical spinal cord, so that disorder of 

 respiration may occur from lesions in these points as well as in 

 the main oblongata centre. 



Respiratory Inhibition and arrest depend on the vagus, the 

 superior and inferior laryngeal nerves. 



The Salivation Centre also lies in the floor of the fourth 

 ventricle and stimulation of the medulla causes free secretion. 



The Centres for Sneezing, Coughing, Sucking, Chewing, 

 Swallowing and Vomiting are also seated in the oblongata, so 

 that any one of these phenomena may come from a central irrita- 

 tion. In bulbar paralysis the loss of power usually extends from 

 the tongue through the lips, cheeks, jaws, pharynx, larynx, to 

 the respiratory muscles and heart. Coughing may be roused by 

 irritation of the external auditory meatus, liver, stomach, bowels, 

 or generative organs as well as from the air passages. 



Cardiac Accelerating and Inhibiting Centres are both 

 present in the bulb, the latter receiving its afferent impulse main- 

 ly through the vagus nerve. Stimulation of the vagi, anaemia of 

 the bulb through decapitation or through tying both carotids, 

 hjrpersemia through tying of the jugulars, a venous state of the 

 blood, and blows on the abdomen all slow or arrest the heart 

 action. Digitalis or muscarin has a similar effect. The heart 

 action is accelerated by febrile and inflammatory affections, by 

 a high or low temperature by section of the vagi, by sipping 

 of cold water, by atropine or curari, and by salts of soda. Potash 

 salts on the other hand restore the inhibitory action of the vagi 

 and lower the heart's action. 



The Vaso Motor Centre is also in the oblongata and the 

 contraction of the vessels with increase of arterial pressure may 

 ensue from afferent currents in the sympathetic nerve and many 

 sensory trunks. The varying activity is seen in blushing, in the 

 congestion of mucous membranes under rage or excitement, in the 

 capillary contraction in the early stage of inflammation, in the 

 second stage of capillary dilation, in angioma, or nsevus, and in 

 extensive congestions and haemorrhages in different organs. The 

 arrest of bleeding under fainting is due largely to the anaemia of 

 this centre. 



A Spasm Centre the pricking of which causes general con- 

 vulsions lies in the medulla oblongata at its junction with the 



