406 DISEASES CLASS IV. 2. 1. 11. 



is now lessened by their reverse sympathy with that of the heart 

 and arteries. See Supplement, I. 8. 



11. Vertigo visualis. Visual vertigo. The vertigo rotatoria 

 described above, was induced by the rotation or undulation of 

 external objects, and was attended with increased action of the 

 primary link of the associated motions belonging to vision, and 

 with consequent pleasure. The vertigo visualis is owing to less 

 perfect vision, and is not accompanied with pleasurable sensa- 

 tion. This frequently occurs in strokes of the palsy, and is then 

 succeeded by vomiting; it sometimes precedes epileptic fits, 

 and often attends those, whose sight begins to be impaired by 

 age. 



In this vertigo the irritative ideas of the apparent motions of 

 objects are less distinct, and on that account are not succeeded 

 by their usual irritative associations of motion; but excite our 

 attention. Whence the objects appear to librate or circulate 

 according to the motions of our heads, which is called dizziness; 

 and we lose the means of balancing ourselves, or preserving our 

 perpendicularity, by vision. So that in this vertigo the motions 

 of the associated organs are decreased by direct sympathy with 

 their primary link of irritation; as in the preceding case of sea- 

 sickness they are decreased by reverse sympathy. 



When vertigo affects people about fifty years of age, their 

 sight has generally been suddenly impaired; and from their less 

 accurate vision they do not soon enough perceive the apparent 

 motions of objects; like a person in a room, the walls of which 

 are stained with the uniform figures of lozenges, explained in 

 Sect. XX. 1. This is generally ascribed to indigestion; but it 

 ceases spontaneously as the patient acquires the habit of balanc- 

 ing himself by less distinct objects. 



A gentlemen about 50 was seized with an uncommon degree 

 of vertigo, so as to fall on the ground, and not be able to turn 

 his head, as he sat up either in his chair or in his bed, and this 

 continued eight or ten weeks. As he had many decayed teeth 

 in his mouth, and the vertigo was preceded and sometimes ac- 

 companied by pains on one side of his head, the disease of a 

 tooth was suspected to be the cause. And as his timidity was 

 too great to admit the extraction of those which were de- 

 cayed; after the trial of cupping repeatedly, fomentations on 

 his head, repeated blisters, with valerian, Peruvian bark, musk, 

 opium, and variety of other medicines; mercurials were used, 

 both externally and internally, with design to inflame the mem- 

 branes of the teeth, and by that means to prevent the torpor of 

 the action of the membranes about the temple, and parietal bone; 

 which are catenated with the membranes of the teeth by irrita- 



