THE SEMICIRCULAR CANALS. 1205 



These experiments undoubtedly prove that the ampullae contain 

 sense organs connected with the sense of equilibrium. Lee is of 

 opinion that the otoliths and maculae form the organ for statical 

 equilibrium. 



The light thrown upon the subject by pathological evidence is scanty. 

 There is no doubt that any disease or injury of these structures, 

 occurring rapidly, produces giddiness, staggering, nystagmus, vomiting, 

 noises in the ears, and more or less deafness, though sometimes some 

 of the symptoms may be absent. But all these, with the exception of 

 the deafness, may merely be reflex symptoms, and even the deafness is 

 probably due to coincident affection of the cochlea. 



On the other hand, a slowly progressive affection of the labyrinth 

 may ultimately leave the canals and vestibule transformed into a bony 

 mass, in which no trace of the original soft structures remains. In 

 such cases there may be no perceptible disturbance of equilibrium, no 

 nystagmus or giddiness, nor any other symptom of that nature. 1 If, 

 therefore, we look upon the canals and vestibule as organs whose 

 function is the maintenance of equilibrium, then we must admit that 

 they are not indispensable for that purpose, but that some other organ 

 is able to carry on the function. 



From the foregoing, it will be seen that the subject is involved in 

 obscurity. Certain symptoms follow injury to the canals, such as loss 

 of equilibrium, giddiness, nystagmus, and often vomiting ; and we may 

 assume that these symptoms are not due to coincident injury of the 

 brain. Injury to the cochlea produces no such symptoms. Are we to 

 conclude, therefore, that the function of the former structures is to 

 make us conscious of the position of the head in space, or the main- 

 tenance of equilibrium, or the maintenance of muscular tone, etc. ? 

 One difficulty lies in the fact that all the symptoms may be merely 

 reflexes caused by injury, and may not be due to loss of function. The 

 vestibular nerve is in much closer connection than the cochlear portion 

 with those regions of the central nervous system (such as the cerebellum) 

 which, when injured, cause such symptoms. 



Whether the canals are concerned in the act of hearing is not 

 known. Injury to these structures in animals does not appear to cause 

 deafness, but we cannot definitely say that hearing is unaffected. In 

 the human subject, on the other hand, it is extremely doubtful whether 

 the canals and vestibule are ever affected without causing deafness; 

 but it must be remembered that these structures are rarely affected 

 without the cochlea suffering coincidently, so that the deafness may be 

 caused by disease of the latter structure. 2 



1 Politzer, " Diseases of the Ear," 1894, p. 606. 



2 A precis of the enormous literature on the functions of the semicircular canals is 

 given by von Stein, op. cit., S. 172-522. He has collected the results of many investigations, 

 and although the material is presented in considerable confusion, the book is a mine of 

 literary wealth. 



