CHAP. XI.] VERTIGO. 369 



or in the quality of the blood sent to the brain. A sensation 

 of a rushing of blood to the head is often consequent upon excessive 

 hemorrhage, or accompanies a state of extreme debility from any 

 cause. This is owing in great part to the feeble tone of the arte- 

 ries, resisting imperfectly the flow of blood to the head, and allow- 

 ing it to impress the nervous matter too much. It is well known, 

 that, by turning round quickly on one's own axis, the sense of 'vertigo 

 may be produced, a confused feeling in the head, and an inability 

 to maintain perfectly the balance of the body, accompanied by an ap- 

 pearance as if external objects were revolving. If the eyes be kept 

 shut, the uneasy feelingof the head will take place, but no true vertigo. 

 To obtain this feeling perfectly, the eyes must be open, and objects 

 presented to them. And Purkinje has shewn that the direction in 

 which external objects appear to revolve is influenced by the position 

 of the body and of the head while turning round, and by the position 

 of it afterwards, when the experimenter has ceased to move round. 

 If the experimenter have kept his head in the vertical position while 

 moving round, and afterwards when standing still, the objects ap- 

 pear to revolve in the horizontal direction. If the head be held 

 with the occiput upwards while turning round, and then erect when 

 standing still, the objects seem to rotate in a vertical plane, like a 

 wheel placed vertically revolving round its axis.* It is highly 

 probable that these sensations, as well as those which arise spon- 

 taneously, are due to some irregular distribution of blood to various 

 parts of the brain. A sense of giddiness frequently precedes faint- 

 ing, and is attributable to the temporary deficiency in the supply of 

 blood to the head. If the horizontal position be immediately 

 adopted, or the body be laid with the head inclined downwards, the 

 faint may be prevented. The sense of giddiness which is expe- 

 rienced upon rising from the horizontal position after illness, is 

 doubtless of the same kind. Anaemic patients experience this feel- 

 ing of giddiness even in the horizontal posture; and both it and 

 the headache and delirium, which accompany this state of bloodless- 

 ness, may be somewhat relieved by placing the patient on an in- 

 clined plane with the head downwards. 



The mind possesses a remarkable power of exciting and of exalt- 

 ing painful sensations in various parts of the body. If the attention 

 be directed very strongly, and for some time, to any part, that part 

 may become the seat of pain, for which the most effective remedy 

 is to engage the thoughts as much as possible on some other object, 



* Miiller's Physiology, by Baly, vol.i. p. 848. 



B B 



