14 THE HISTOGENESIS AND GROWTH OF THE OTIC CAPSULE AND ITS 



the labyrinth, and the cell tissue intervening between these. This intervening tissue 

 undergoes an independent growth characterized by a rich growth of blood-vessels. 

 As a space, i. e., the cavity of the cartilago petrosa, it grows in correspondence 

 to the growth of the epithelial labyrinth. As to the behavior of the cartilage 

 during the growth Kolliker was undecided, giving the opinion, however, that it grew 

 independently at the same time as the space, and was not simply mechanically 

 stretched out. 



The embryological studies of His began to appear at about the time of the pub- 

 lication of Kolliker's work on the ear, and one would rather expect that the attention 

 of this keen observer would have been attracted to this subject. In his "Akade- 

 mische Programme" of the year 1865 he outlines (His, 1903) the general problem of 

 the formation of the various body-cavities and describes in detail the formation 

 of the cavities of the middle germ-layer. He includes in this the arachnoid spaces 

 and the cavities of the eye-ball, but he does not refer to the ear. 



Inasmuch as the present paper is directly concerned only with the capsule of 

 the ear and the contained periotic connective-tissue spaces, it will not be necessary 

 to trace the further elaboration of a more precise knowledge of the structure of the 

 membranous labyrinth which rapidly took place following the appearance of Kol- 

 iker's text-book and the introduction of the new histological and embryological 

 methods which were devised in such abundance at about that time. A complete 

 survey of such investigations is given in the monograph of Retzius (1884), to 

 which the reader is referred. Our review here of the subsequent literature will be 

 restricted to those publications having a special bearing on the periotic connective- 

 tissue structures and the problem of their development. 



The canalis reuniens was discovered by Hensen (1863) as a communication exist- 

 ing between the ductus cochlearis and the sacculus. This established the relation 

 of the cochlear duct as a definite part of the closed system of the membranous laby- 

 rinth, and its complete separation from the vestibular space. Using the terminology 

 of Breschet, it thus constitutes an endolymphatic space, whereas the scala vestibuli 

 and seal atympani are both perilymphatic spaces. Hensen also described the aquae- 

 ductus cochleae. He regarded it as an invagination from the outer perichondrium 

 into the cochlea by a process similar to the invagination of the aqueous humor of the 

 eye. In the embryo it consists of a connective-tissue tube which is continuous with 

 the primary periosteum. It splits into two limbs, the shorter one of which extends 

 towards the round window and forms the lining of the proximal part of the scala 

 tympani. The other limb of the membranous aqueduct extends towards the modio- 

 lus and unites with the dura mater of the acoustic nerve. 



Hensen was followed by Odenius (1867) who gives a careful description of 

 the position of the different parts of the membranous labyrinth and of the "peri- 

 lymphatic " spaces surrounding them. He separates the perilymphatic space of the 

 vestibule into two divisions based on the attachment of the utricle to the vestibular 

 wall. The lower and chief division he names sinus perilymphaticus vestibuli. This 

 communicates with the upper division, which surrounds the upper part of the utricle 

 and extends along the semicircular canals. This part is narrower and is hardly 



