406 DISEASES CLASS IV. 2.1.11. 



is now leffened by their reverfe fympathy with that of the hearfc 

 and arteries. See Supplement, I. 8. 



1 1 . Fertigo vifualis. Vifual vertigo. The vertigo rotatoria 

 defcribed above, was induced by the rotation or undulation of 

 external objects, and was attended with increafed action of the 

 primary link of the ailbciated motions belonging to vifion, and 

 with confequent pleafure. The vertigo vifualis is owing to lefs 

 perfect vifion, and is not accompanied with pleafurable fenfa- 

 tion. This frequently occurs in ftrokes of the palfy, and is then 

 fucceeded by vomiting ; it fometimes precedes epileptic fits, 

 and often attends thofe, whofe fight begins to be impaired by 

 age. 



In this vertigo the irritative ideas of the apparent motions of 

 objects are lefs diftinct, and on that account are not fucceeded 

 by their ufual irritative afibciations of motion ; but excite our 

 attention. Whence the objects appear to librate or circulate 

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

 and we lofe the means of balancing ourtelves, or preferving our 

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

 of the aflbciated organs are decreafed by direct fympathy with 

 their primary link of irritation ; as in the preceding cafe of fea- 

 (icknefs they are decreafed by reverfe fympathy. 



When vertigo affects people about fifty years of age, their 

 fight has generally been fuddenly impaired ; and from their lefs 

 accurate vifion they do not foon enough perceive the apparent 

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

 are ftained with the uniform figures of lozenges, explained in 

 Sect. XX. i. This is generally afcribed to indigeftion ; but it 

 ceafes fpontaneoufly, as the patient acquires the habit of balanc- 

 ing himfelf by lefs diftinct objects. 



A gentleman about 50 was feized with an uncommon degree 

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

 his head, as he fat 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 fometimes ac- 

 companied by pains on one fide of his head, the difeafe of a 

 tooth was fufpected to be the caufe. And as his timidity was 

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

 cayed ; after the trial of cupping repeatedly, fomentations on 

 his head, repeated blifters, with valerian, Peruvian bark, mufk, 

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

 both externally and internally, with defign 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-- 



tive 



