268 OUTPOSTS OF THE INTELLIGENCE SERVICE 



saccule through the ductus cndohjiuphuticus, and the saccule into 

 the scala media through the cattali.s rcunicns. Ner\'e fibres from 

 the vestibular division of the auditory nerve end in naked fibrils 

 between the hair-cells of the maculae of the utricle and saccule 

 and of the cristae ampullares of the semicircular ducts. The 

 maculae and cristae are little thickenings on the internal surfaces 

 of these cavities, one in each. The epithelium on the surface of 

 the humps is columnar, and consists of (i.) fusiform supporting 

 cells, the free ends of which unite to form a thin cuticle, and 

 (ii.) flask-shaped hair-cells, whose free ends are surmounted by a 

 long, tapering, hair-like filament. Two small rounded calcareous 

 bodies termed otoconia, or otoliths, lie in contact with the free 

 ends of the projecting hairs of the maculae. 



Mechanism of Utricles and Saccules. 



It is obvious that any movement of the hairs will cause a 



Fig. 68. — Eabbit's skull with oriented magnified models of the utricle and saccule 

 maculae. Skull in normal position. The suriface of the macula to which the otolith is 

 attached is indicated in the utricle by white dots and in the saccula by white stripes on the 

 black I'late. Stereoscopic. (Magnus, " Korperstellung.") 



stimulation of the filaments of the vestibular nerve, and that the 

 otoliths are an excellent means of providing this stimulation. 

 But the exact way in which this occurs does not appear to be so 

 simple a matter to determine. The literature on this question 

 contains somewhere about 2,000 papers, and they do not all 

 convey the same impression. To begin with, most of the work has 

 been done on fishes, where operative procedure is simpler than in 

 the mammal. One cannot directly apply knowledge so gained to 

 the human being, because the structure and function of the organs 

 are somewhat different. The present ^'iew, largely due to experi- 

 ments on the rabbit and other manmials by Magnus, is that an 

 alteration of the position of the head brought about by allowing 

 gravity to act on the otoliths causes them to exert a slight pull on 

 the hairs, and so to induce the passage of a nervous impulse which 

 in turn affects the muscular tone of the body. 



Utricles. The utricle in each ear has one macula with its otolith. 



