74 Veterinary Medichie. 



other hand any injury to the canals, by disturbing the pressure 

 of the perilymph and interfering with the relative position of the 

 canals, and the direction and force of the currents of the endo- 

 lymph and perilymph, destroys all proper sense of balance. 

 The rotation of the subject as on a wheel or in turning in a 

 narrow circle, is held to cause circular currents in and around 

 the membranous labyrinth which temporarily destroy all sense of 

 equilibrium. Seasickness and railroad sickness are doubtless in 

 part due to the swaying motions causing disturbance in the 

 canals. The intimate relation between the root of the auditory 

 .nerve and that of the vagus in the medulla, may serve to explain 

 the mutual interdependence of derangement of the stomach and 

 liver on the one hand and the occurrence of vertigo on the other. 

 Again the relation of vertigo to visual troubles, both as to cause 

 and effect, has been attributed to the close relations of the 

 ganglia presiding over the 3d, 4th. 5th and 6th nerves and those 

 of the nerve of hearing. 



There is a degree of deafness in nearly all cases of aural verti- 

 go, a circumstance which may be utilized in the diagnosis of such 

 cases, the presence of disease of the guttural pouch, or Eusta- 

 chian tube, and evidence of deafness on one side rather than the 

 other, may be taken as corroborative evidence of the affection. 

 On the other hand James shows that the stone deaf are much 

 less subject to both seasickness and vertigo than tiiose that hear. 

 The disorder that leads to vertigo implies a retention of a meas- 

 ure of the normal function of the internal ear, and therefore of 

 hearing, whereas the disease that has caused complete destruction 

 of the internal ear and consequent loss of hearing has equally 

 destroyed the function of the labyrinth in maintaining a sense of 

 balance, and has obviated the aural sensations of equilibrium and 

 loss of balance. 



8th. Cerebral Vertigo may be associated with derangement 

 of the circulation, or disease in the brain or its meninges. 

 Anaemias and congestions resulting from disease or impaired 

 function of heart, lungs, arteries or veins have been already 

 noticed. It remains to note the presence of cholesteatomata and 

 other tumors, and of parasites (cysticercus cellulosa in pig ; 

 coenurus cerebralis in sheep) in the encephalon, and of injuries 

 from concussion, degeneration and softening of the brain sub- 

 .stance. 



