ORGANS OF THE SENSES. 531 



parent, and exhibits in parts a longitudinal fibrillation ; treated 

 with acetic acid, it presents numerous corpuscles or cell nuclei. 

 Where it is thinnest it has a near resemblance to the hyaloid 

 membrane of the eye. The internal coat is composed of nu- 

 cleated particles, closely opposed, and but slightly adherent ; 

 the nuclei are often saucer-shaped, and when seen edgeways 

 have the uncommon appearance of a crescent. They easily 

 become detached and fall into the endolymph. Minute 

 arteries and veins, derived chiefly from a branch of the ba- 

 sillar accompanying the auditory nerve, enter the vestibule 

 from the internal meatus, and ramify on the exterior of the 

 membranous labyrinth, apparently bathed in the perilymph. 

 A beautiful network of capillaries, forcibly reminding the 

 observer of that belonging to the retina, is spread out on the 

 outer surface and in the substance of the proper coat. These 

 vessels have the simple homogeneous wall interspersed here 

 and there with cell nuclei, that characterises the capillary 

 channels in many other situations. There is an abundant 

 network of capillaries in the interior of the utriculus and 

 sacculus, about the terminal distribution of the nerves, which 

 evinces the activity of the functions of these parts. 



" The membranous labyrinth, or its simple representative 

 the auditory sac, contains in all animals either solid or pulve- 

 rulent calcareous matter in connection with the termination of 

 the vestibular nerves. This has been called by Breschet 

 otolith or earstone, when solid, as in the osseous fishes, and 

 otoconia or ear-powder, when in the form of minute crys- 

 talline grains, as in Mammalia, birds, and reptiles ; but the 

 former term may be conveniently employed to designate both 

 varieties. In the Mammalia, including man, it is found ac- 

 cumulated in small masses about the termination of the nerves, 

 both in the utriculus and sacculus, and we have found it also 

 sparingly scattered in the cells lining the ampulla? and semi- 

 circular canals. In the vestibular sacs it appears to be en- 

 tangled in a mesh of very delicate branched fibrous tissue, in 

 connection with the wall, and it is most probably held in place 

 by cells within which, according to Krieger *, its particles 



* De Otolithis. Berol, 1840. 



