254 



AYERS. [Vol. VI . 



impulses other than those of sight, touch, and the muscular 

 sense do reach the brain and afford a basis of judgment as to 

 the position of the body, does not by itself prove that those 

 impulses come from the semicircular canals ; the arrangement 

 of the canals is undoubtedly suggestive [italics mine] ; but it is 

 quite possible that the afferent impulses may be generated by 

 one or other of various changes, vaso-motor and others, of the 

 tissues of the body which are involved in a change of position." 

 " It cannot, therefore, be regarded as settled that the canals 

 are the source of normal impulses, or that our conscious appre- 

 ciation of the position of the head, and so of the body in space, 

 is based on such impulses." " But such a view is not disproved ; 

 and in any case it remains true that injury to the canals does 

 in some way or other, either by generating new impulses or 

 by altering pre-existing ones, so modify the flow of afferent 

 impulses into the machinery of co-ordination as to throw that 

 machinery out of gear." 



M'Kendrick (1889) on p. 701 says, after stating Cyon's posi- 

 tion in 1872, according to which the latter investigator consid- 

 ered the cristse acusticse to be the peripheral spatial sense organs, 

 the cristas of each set of canals, e.g. the two externals, controll- 

 ing a dimension of space, that " the weakness of Cyon's theory 

 is that it offers no explanation of the mechanism of the canals." 



We now come to the colophon, P. McBride, M.P., has pub- 

 lished his views of the functions of the semicircular canals, 

 obtained, it would seem, "durch eine Seitenthiire," if Goethe 

 was just in asserting that science has daily to suffer from 

 such architects. McBride's plan of the structural relations of 

 the semicircular canals is constructeH in the following manner. 

 After showing to his satisfaction that the Cyon-Mach-Breuer- 

 Crum Brown theory, according to which they (the canals) are 

 the peripheral organs enabling us to estimate our position in 

 space, is insufficient and inconsistent, he says we should admit 

 " nothing in life is superfluous," and that " every physiological 

 apparatus is the best possible for the well-being of the organism," 

 and that in the animal economy " there is reason for every ana- 

 tomical detail." The first of these statements is so extensive 

 in its application as to overwhelm any but the greatest intellects, 

 and is for the most part left undecided by experimentalists, 

 while the second proposition is certainly not to be classed 



