406 SPECIAL HISTOLOGY. 



pigment- cells. This is succeeded by a transparent, glassy 

 membrane, sharply defined, especially on the inner aspect, 

 0*004 — O'OOS'" thick, presenting in parts a distinct, delicate, 

 longitudinal striation, and on the addition of acetic acid always 

 exhibiting a multitude of elongated nuclei, and which con- 

 sequently cannot well be placed in the same class with the 

 membrance propria, the capsule of the lens, &c, although it very 

 nearly approaches them in its chemical reactions. The inner- 

 most layer, lastly, is a simple, readily disintegrated, tesselated 

 epithelium, 0*003'", with sometimes larger, sometimes smaller 

 (0*004 — 0*008'") polygonal cells, lining all the spaces in 

 question, and inclosing the so-termed endolymph. s. aquula 

 vitrea auditiva, in which, in Fishes, Barruel has ascertained 

 the presence of mucus. 



The vessels of the membranous labyrinth are tolerably nu- 

 merous, and are distributed in minute arteries and veins and 

 abundant capillary net-works, on the fibrous membrane and 

 vitreous tunic of these parts, being most abundant near the 

 terminations of the nerves. Of these, we are acquainted only 

 with that of the acoustic nerve, which, with the nervus vestibuli, 

 supplies the three membranous canals and the elliptic sacculus, 

 and, with a branch of the cochlear nerve, the round sacculus. 

 In the semicircular canals, the nerves are distributed only on 

 the ampulla, and, indeed, enter each, as Steifensand has shown, 

 in an inversion or duplicature of the wall situated on the con- 

 cave side of the canal, which appears, viewed on the inside, as 

 a transverse projection extending through about one third of 

 the circumference. Within these folds, the nerves divide at 

 first into two principal branches, which, diverging towards 

 both sides, penetrate into the vitreous membrane of the 

 ampulla, where each of them breaks up into a rich bundle of 

 smaller, frequently anastomosing ramuscules, which ultimately 

 appear to terminate free, in fine twigs, composed of from two 

 to ten primitive fibres, 0*001 — 0*0015"' thick. In the sacculi, 

 the distribution of the nerves is the same, except that it occu- 

 pies a larger space, and does not occur in a projection of the 

 wall. In this situation, also, I think I have noticed free pro- 

 longations of the attenuated nerves, although it may be very 

 possible, as Todd and Bowman point out, that they are con- 

 tinuous with very pale fibrils, in which they ultimately ter- 



