XXVIII.] THE EAR. 293 



4. At the lower part of the utriculus and sacculus 

 note the white calcareous paste, lift up the 

 membranous bag and note that beneath the 

 paste, nerve fibres enter through the cartilage. 

 Remove the membranous vestibule and canals, 

 sop up any fluid with a sponge and moisten the 

 cartilaginous vestibule and canals with osmic 

 acid; in a short time the nerve fibres entering 

 through the cartilage become blackened and so 

 very distinct. 



5. Trace towards the brain, cutting through the 

 cartilage, one of the nerve bundles, e.g. that 

 entering the utriculus. 



6. Lay bare the semicircular canals in a fresh skate 

 and cut out an ampulla as in 3 ; place it in 

 picric acid or in chromic acid *2 p.c. for a week, 

 treat with alcohol, stain with hsematoxylin, and 

 imbed, soaking previously a short time in the 

 imbedding mixture, clear the sections on the 

 slide and mount in Canada balsam. 



In sections through the crista acustica observe 



a. The outer loose connective tissue, and 



b. The thick connective tissue wall 



c. The numerous large nerve fibres running 

 from the outside towards this; the fibres 

 may be traced through the membrane be- 

 coming much smaller and some losing their 

 medulla. 



